Make CompilerType safe [Was: Add a check for TypeSystem use-after-free problems]

[aprantl]

Summary

Make CompilerType safe

When a process gets restarted TypeSystem objects associated with it
may get deleted, and any CompilerType objects holding on to a
reference to that type system are a use-after-free in waiting. Because
of the SBAPI, we don't have tight control over where CompilerTypes go
and when they are used. This is particularly a problem in the Swift
plugin, where the scratch TypeSystem can be restarted while the
process is still running. The Swift plugin has a lock to prevent
abuse, but where there's a lock there can be bugs.

This patch changes CompilerType to store a std::weak_ptr<TypeSystem>.
Most of the std::weak_ptr<TypeSystem>* uglyness is hidden by
introducing a wrapper class CompilerType::WrappedTypeSystem that has a
dyn_cast_or_null() method. The only sites that need to know about the
weak pointer implementation detail are the ones that deal with
creating TypeSystems.

rdar://101505232

[hawkinsw]

There are *so* many reasons that I love this patch.

First and foremost: I am a professor of computer science at University of Cincinnati and teaching Programming Languages this semester and I am about to teach *this very technique* for protecting against use-after-free errors. Having seen this patch I now have a great example of where it is used in real life! So, thank you!

Second, I have left some comments but please take what I said with a grain of salt. I hope that it is helpful and not a waste of time.

Thank you!
Will

lldb/source/Symbol/CompilerType.cpp

33

I am sorry if this is obvious, but is CompilerType used in a multithreaded environment? So, is there a possibility that we could pass the check on line 32 but become invalid by the use of m_type_system here and fall victim to an attempt (in Lookup, perhaps?) to dereference a NULL pointer? Again, I am sorry if that is a stupid question!

34

I know that this is a nit, but should we write TypeSystem?

lldb/source/Symbol/TypeSystem.cpp

22

I spent *way* too long researching to make sure that this initialization is thread safe and wanted to drop a link here in case anyone is wondering the same thing:

C++ standard: stmt.dcl para 3, sentence 3

[aprantl]

lldb/source/Symbol/CompilerType.cpp

33

Yes, CompilerType could be used on any thread and this will not catch a use-after-free if the TypeSystem is deleted between the IsValid check and its use.

A solution would be to store a TypeSystemSP/WP in CompilerType, but I'm expecting this to be rather expensive. The intention of this patch is as a bug-finding tool. It's not intended to make holding on to CompilerType objects safe. That said, I'm open to explore ideas for how to efficiently make this safe in a future patch.

[labath]

The Halloween theme is nice, but I think it'd be more traditional if we kept a list of active instances, instead of inactive ones. That said, a part of me dies every time I see a class keeping a list of its instances.

I don't know if you've seen it, but I think the Module::m_old_symfiles member exists for the very same reason, and it could be why this does not happen so often outside of swift (which, I believe, stores most of its types in the target type system instead of the module systems).

lldb/source/Symbol/CompilerType.cpp

33

Well.. if you're only interested in SB uses, then I'd say that the SBType object should hold an SP/WP on the type system or some parent of it.

[aprantl]

All right! After @hawkinsw raised the question whether my previous patch didn't still allow for race conditions and some off-line encouragement from @JDevlieghere, I decided to give it a try and properly design away the issue.

This new patch turns the type system stored by CompilerType into weak pointer. Weak pointers use up two pointers as storage so to avoid blowing up the memory footprint, each TypeSystem is now required to have a canonical weak pointer that is never freed. This is implemented as a vector of unique pointers to weak pointers in TypeSystemMap.

This makes all calls to CompilerType completely safe, and CompilerType::GetTypeSystem now returns a nullable shared pointer to the type system. Calls into CompilerType become slower by one pointer lookup and one atomic increment operation, which will likely not be measurable.

Code that call GetTypeSystem() can remain almost unchanged, it just needs to store the shared pointer in a local variable first.

Code that creates a new ad-hoc TypeSystem gets slightly more complex, and I admit I was surprised at how many places in LLDB actually do this.

Please take another look, I think this is much better!

[labath]

Well... like they say, there's no software engineering problem that can't be solved by adding an extra layer of indirection.

In this case, that's "adding an extra layer and leaking it", so I'm wondering if we can drop the second part. I'm going to assume that we want to preserve sizeof(ptr<TypeSystem>), even though I'm not entirely convinced that this would cause a significant increase in our memory footprint.

An ideal solution for this would be a IntrusiveRefCntPtr, but with weak pointer support. That doesn't exist right now, but since we're already adding a layer of indirection, I think that layer could be used to introduce weak semantics. Instead of this "canonical" TypeSystemWP *, we could pass around a IntrusiveRefCntPtr<TypeSystemHolder>, where TypeSystemHolder is essentially a TypeSystemWP wrapped in a ThreadSafeRefCountedBase. I think this doesn't increase the number of dereferences (it's still takes two derefs to get from this funky representation to an actual type system), but it has the advantage that the type system holder will go away when/if all references to it are gone. Another advantage (I hope) could be that we don't see this funky double deref (TypeSystemWP *) pattern everywhere, as it's helpfully hidden in the holder class.

[aprantl]

I have an updated patch here that I started working on before I saw Pavel's comment.

This version removes a lot of the std::weak_ptr<TypeSystem>* uglyness by introducing a wrapper class CompilerType::ManagedTypeSystem that has a dyn_cast_or_null() method and hides the fact that we store weak pointers in CompilerType. Now the only sites that need to know about the weak pointer implementation detail are the ones that deal with creating TypeSystems.

Meanwhile I did some unscientific measurements of attaching LLDB to LLDB and running a few expressions and any difference that an extra pointer in CompilerType makes is smaller than the difference between subsequent runs.

Based on that I'm going to rework this now to just store a WP in CompilerType directly, while still returning a wrapper object with a convenient dyn_cast method. That should be the best of both worlds.

[aprantl]

Here is the greatly simplified version of the patch that just stores a std::weak_ptr<TypeSystem> in CompilerType.
As mentioned earlier the memory increase is entirely within thew noise.

[JDevlieghere]

I like the new approach, it's much easier to follow. I also like the wrapper class to abstract over the common operations. It just seems like there are some remnants of the canonical wp approach that we no longer need.

lldb/include/lldb/Symbol/CompilerType.h

51

nit: lldb::TypeSystemSP m_typesystem_sp = {}; or even lldb::TypeSystemSP m_typesystem_sp

58–60

If it's a dyn_cast_or_null why not do the m_typesystem_sp check, won't dyn_cast_or_null repeat that for you anyway?

lldb/include/lldb/Symbol/TypeSystem.h

88–91

Now that the weak pointer is no longer "canonical", there's no reason that this should be a reference anymore, right?

517–522

Do we still need this? I assume we can now just return the weak pointer directly (through shared_from_this)?

550–553

No longer necessary?

[aprantl]

Address feedback from @JDevlieghere !

[aprantl]

Ping @JDevlieghere @labath

[JDevlieghere]

LGTM modulo a few small nits

lldb/include/lldb/Symbol/CompilerType.h

60

Nit: static_cast<bool>(m_typesystem_sp)

lldb/source/API/SBModule.cpp

457

no else after return

502–504

if (CompilerType compiler_type = ts->GetBuiltinTypeByName(name))

[aprantl]

Address nits.

[JDevlieghere]

LGTM!

[labath]

lldb/include/lldb/Symbol/CompilerType.h

58

Maybe do something like this instead:

template <class TypeSystemType> std::shared_ptr<TypeSystemType> dyn_cast_or_null() {
  if (llvm::isa<TypeSystemType>(m_typesystem_sp.get()))
    return std::shared_ptr<TypeSystemType>(m_typesystem_sp, llvm::cast<TypeSystemType>(m_typesystem_sp.get()));
  return nullptr;
}

That said, llvm::dyn_cast supports custom casts for smart pointers (it already has them for std::unique_ptr), so it should be possible to completely avoid this wrapper class by implementing this logic inside llvm.
Although, then we'd have to answer awkward questions like "why are you using a shared_ptr in the first place".

60

add explicit

lldb/include/lldb/Symbol/TypeSystem.h

517–520

Can this be replaced by inheriting from std::enable_shared_from_this?

lldb/source/Core/DumpDataExtractor.cpp

322

why?

[aprantl]

Address (excellent) feedback from @labath!

lldb/include/lldb/Symbol/CompilerType.h

58

I think that's a good idea. Based on the assumption that we are going to rework the ownership model in LLDB to move away from shared pointers towards contexts at some point in the future, I'm not going to extend casting support in Support now.

[labath]

Some more comments inline, but I think this is essentially as good as we can make it.

lldb/include/lldb/Symbol/Type.h

300

Maybe the wrapper type should just be its own top-level entity? Or TypeSystem::SPWrapper?

lldb/source/Plugins/Platform/FreeBSD/PlatformFreeBSD.cpp

193–194

Remove m_type_system, change m_type_system_sp to std::shared_ptr<TypeSystemClang>

lldb/source/Plugins/Platform/Linux/PlatformLinux.cpp

316–321

Same here (but also remove the _wp variable).

lldb/source/Plugins/Platform/NetBSD/PlatformNetBSD.cpp

211

and here

lldb/source/Symbol/TypeSystem.cpp

276–278

With the current implementation, I don't think these can ever fire.

lldb/source/Target/Target.cpp

2461

Maybe this error needs some updating? (also, missing spaces -- the language will get glued to the error msg)

lldb/unittests/TestingSupport/Symbol/ClangTestUtils.h

48

Can this be replaced by a shared_ptr<TypeSystemClang> now?

[aprantl]

lldb/include/lldb/Symbol/Type.h

300

I tried it and then immediately undid it because TypeSystem.h already depends on CompilerType.h.

[stella.stamenova]

Looks like this broke the windows lldb bot: https://lab.llvm.org/buildbot/#/builders/83/builds/26042

[stella.stamenova]

Looks like the windows lldb bot is still broken: https://lab.llvm.org/buildbot/#/builders/83/builds/26083

[aprantl]

In D136650#3932481, @stella.stamenova wrote:

Looks like this broke the windows lldb bot: https://lab.llvm.org/buildbot/#/builders/83/builds/26042

I'm trying to fix this blindly. Should hopefully work after a few iterations.

[aprantl]

I think it's fixed now.

lldb/include/lldb/Core/Module.h

public:
   uint32_t ResolveSymbolContextsForFileSpec(
       const FileSpec &file_spec, uint32_t line, bool check_inlines,
       lldb::SymbolContextItem resolve_scope, SymbolContextList &sc_list);
 
   void SetFileSpecAndObjectName(const FileSpec &file, ConstString object_name);
 
   bool GetIsDynamicLinkEditor();
 
-  llvm::Expected<TypeSystem &>
+  llvm::Expected<lldb::TypeSystemSP>
   GetTypeSystemForLanguage(lldb::LanguageType language);
 
-  void ForEachTypeSystem(llvm::function_ref<bool(TypeSystem *)> callback);
+  void ForEachTypeSystem(llvm::function_ref<bool(lldb::TypeSystemSP)> callback);
 
   // Special error functions that can do printf style formatting that will
   // prepend the message with something appropriate for this module (like the
   // architecture, path and object name (if any)). This centralizes code so
   // that everyone doesn't need to format their error and log messages on their
   // own and keeps the output a bit more consistent.
   void LogMessage(Log *log, const char *format, ...)
       __attribute__((format(printf, 3, 4)));

lldb/include/lldb/Symbol/CompilerType.h

 #define LLDB_SYMBOL_COMPILERTYPE_H
 
 #include <functional>
 #include <string>
 #include <vector>
 
 #include "lldb/lldb-private.h"
 #include "llvm/ADT/APSInt.h"
+#include "llvm/Support/Casting.h"
 
 namespace lldb_private {
 
 class DataExtractor;
+class TypeSystem;
 
 /// Generic representation of a type in a programming language.
 ///
 /// This class serves as an abstraction for a type inside one of the TypeSystems
 /// implemented by the language plugins. It does not have any actual logic in it
 /// but only stores an opaque pointer and a pointer to the TypeSystem that
 /// gives meaning to this opaque pointer. All methods of this class should call
 /// their respective method in the TypeSystem interface and pass the opaque
 /// pointer along.
 ///
 /// \see lldb_private::TypeSystem
 class CompilerType {
 public:
   /// Creates a CompilerType with the given TypeSystem and opaque compiler type.
   ///
   /// This constructor should only be called from the respective TypeSystem
   /// implementation.
   ///
   /// \see lldb_private::TypeSystemClang::GetType(clang::QualType)
-  CompilerType(TypeSystem *type_system, lldb::opaque_compiler_type_t type)
-      : m_type(type), m_type_system(type_system) {
+  CompilerType(lldb::TypeSystemWP type_system,
+               lldb::opaque_compiler_type_t type)
+    : m_type_system(type_system), m_type(type) {
+    assert(Verify() && "verification failed");
+  }
+
+  /// This is a minimal wrapper of a TypeSystem shared pointer as
+  /// returned by CompilerType which conventien dyn_cast support.
+  class TypeSystemSPWrapper {
+    lldb::TypeSystemSP m_typesystem_sp;
+
+  public:
+    TypeSystemSPWrapper() = default;
+    TypeSystemSPWrapper(lldb::TypeSystemSP typesystem_sp)
+        : m_typesystem_sp(typesystem_sp) {}
+
+    template <class TypeSystemType> bool isa_and_nonnull() {
+      if (auto *ts = m_typesystem_sp.get())
+        return llvm::isa<TypeSystemType>(ts);
+      return false;
+    }
+
+    /// Return a shared_ptr<TypeSystemType> if dyn_cast succeeds.
+    template <class TypeSystemType>
+    std::shared_ptr<TypeSystemType> dyn_cast_or_null() {
+      if (isa_and_nonnull<TypeSystemType>())
+        return std::shared_ptr<TypeSystemType>(
+            m_typesystem_sp, llvm::cast<TypeSystemType>(m_typesystem_sp.get()));
+      return nullptr;
+    }
+
+    explicit operator bool() const {
+      return static_cast<bool>(m_typesystem_sp);
+    }
+    bool operator==(const TypeSystemSPWrapper &other) const;
+    bool operator!=(const TypeSystemSPWrapper &other) const {
+      return !(*this == other);
+    }
+
+    /// Only to be used in a one-off situations like
+    ///    if (typesystem && typesystem->method())
+    /// Do not store this pointer!
+    TypeSystem *operator->() const;
+
+    lldb::TypeSystemSP GetSharedPointer() const { return m_typesystem_sp; }
+  };
+
+  CompilerType(TypeSystemSPWrapper type_system, lldb::opaque_compiler_type_t type)
+    : m_type_system(type_system.GetSharedPointer()), m_type(type) {
     assert(Verify() && "verification failed");
   }
 
   CompilerType(const CompilerType &rhs)
-      : m_type(rhs.m_type), m_type_system(rhs.m_type_system) {}
+      : m_type_system(rhs.m_type_system), m_type(rhs.m_type) {}
 
   CompilerType() = default;
 
   /// Operators.
   /// \{
   const CompilerType &operator=(const CompilerType &rhs) {
-    m_type = rhs.m_type;
     m_type_system = rhs.m_type_system;
+    m_type = rhs.m_type;
     return *this;
   }
 
   bool operator<(const CompilerType &rhs) const {
-    if (m_type_system == rhs.m_type_system)
+    auto lts = m_type_system.lock();
+    auto rts = rhs.m_type_system.lock();
+    if (lts.get() == rts.get())
       return m_type < rhs.m_type;
-    return m_type_system < rhs.m_type_system;
+    return lts.get() < rts.get();
   }
   /// \}
 
   /// Tests.
   /// \{
   explicit operator bool() const {
-    return m_type != nullptr && m_type_system != nullptr;
+    return m_type_system.lock() && m_type;
   }
 
-  bool IsValid() const { return m_type != nullptr && m_type_system != nullptr; }
+  bool IsValid() const { return (bool)*this; }
 
   bool IsArrayType(CompilerType *element_type = nullptr,
                    uint64_t *size = nullptr,
                    bool *is_incomplete = nullptr) const;
 
   bool IsVectorType(CompilerType *element_type = nullptr,
                     uint64_t *size = nullptr) const;
 
public:
 
   /// AST related queries.
   /// \{
   size_t GetPointerByteSize() const;
   /// \}
 
   /// Accessors.
   /// \{
-  TypeSystem *GetTypeSystem() const { return m_type_system; }
+
+  /// Returns a shared pointer to the type system. The
+  /// TypeSystem::TypeSystemSPWrapper can be compared for equality.
+  TypeSystemSPWrapper GetTypeSystem() const;
 
   ConstString GetTypeName(bool BaseOnly = false) const;
 
   ConstString GetDisplayTypeName() const;
 
   uint32_t
   GetTypeInfo(CompilerType *pointee_or_element_compiler_type = nullptr) const;
 
   lldb::LanguageType GetMinimumLanguage();
 
   lldb::opaque_compiler_type_t GetOpaqueQualType() const { return m_type; }
 
   lldb::TypeClass GetTypeClass() const;
 
-  void SetCompilerType(TypeSystem *type_system,
+  void SetCompilerType(lldb::TypeSystemWP type_system,
+                       lldb::opaque_compiler_type_t type);
+  void SetCompilerType(TypeSystemSPWrapper type_system,
                        lldb::opaque_compiler_type_t type);
 
   unsigned GetTypeQualifiers() const;
   /// \}
 
   /// Creating related types.
   /// \{
   CompilerType GetArrayElementType(ExecutionContextScope *exe_scope) const;
#endif
   void DumpTypeDescription(Stream *s, lldb::DescriptionLevel level =
                                           lldb::eDescriptionLevelFull) const;
   /// \}
 
   bool GetValueAsScalar(const DataExtractor &data, lldb::offset_t data_offset,
                         size_t data_byte_size, Scalar &value,
                         ExecutionContextScope *exe_scope) const;
   void Clear() {
+    m_type_system = {};
     m_type = nullptr;
-    m_type_system = nullptr;
   }
 
 private:
 #ifndef NDEBUG
   /// If the type is valid, ask the TypeSystem to verify the integrity
   /// of the type to catch CompilerTypes that mix and match invalid
   /// TypeSystem/Opaque type pairs.
   bool Verify() const;
 #endif
 
+  lldb::TypeSystemWP m_type_system;
   lldb::opaque_compiler_type_t m_type = nullptr;
-  TypeSystem *m_type_system = nullptr;
 };
 
 bool operator==(const CompilerType &lhs, const CompilerType &rhs);
 bool operator!=(const CompilerType &lhs, const CompilerType &rhs);
 
 struct CompilerType::IntegralTemplateArgument {
   llvm::APSInt value;
   CompilerType type;
 };
 
 } // namespace lldb_private
 
 #endif // LLDB_SYMBOL_COMPILERTYPE_H

lldb/include/lldb/Symbol/SymbolFile.h

GetMangledNamesForFunction(const std::string &scope_qualified_name,
                              std::vector<ConstString> &mangled_names);
 
   virtual void GetTypes(lldb_private::SymbolContextScope *sc_scope,
                         lldb::TypeClass type_mask,
                         lldb_private::TypeList &type_list) = 0;
 
   virtual void PreloadSymbols();
 
-  virtual llvm::Expected<lldb_private::TypeSystem &>
+  virtual llvm::Expected<lldb::TypeSystemSP>
   GetTypeSystemForLanguage(lldb::LanguageType language) = 0;
 
   virtual CompilerDeclContext
   FindNamespace(ConstString name, const CompilerDeclContext &parent_decl_ctx) {
     return CompilerDeclContext();
   }
 
   virtual ObjectFile *GetObjectFile() = 0;
public:
   /// for this module have been changed.
   void SectionFileAddressesChanged() override;
 
   // Compile Unit function calls
   // Approach 1 - iterator
   uint32_t GetNumCompileUnits() override;
   lldb::CompUnitSP GetCompileUnitAtIndex(uint32_t idx) override;
 
-  llvm::Expected<lldb_private::TypeSystem &>
+  llvm::Expected<lldb::TypeSystemSP>
   GetTypeSystemForLanguage(lldb::LanguageType language) override;
 
   void Dump(Stream &s) override;
 
   uint64_t GetDebugInfoSize() override;
 
   bool GetDebugInfoIndexWasLoadedFromCache() const override {
     return m_index_was_loaded_from_cache;

lldb/include/lldb/Symbol/SymbolFileOnDemand.h

void FindTypes(llvm::ArrayRef<lldb_private::CompilerContext> pattern,
                  lldb_private::LanguageSet languages,
                  llvm::DenseSet<SymbolFile *> &searched_symbol_files,
                  lldb_private::TypeMap &types) override;
 
   void GetTypes(lldb_private::SymbolContextScope *sc_scope,
                 lldb::TypeClass type_mask,
                 lldb_private::TypeList &type_list) override;
 
-  llvm::Expected<lldb_private::TypeSystem &>
+  llvm::Expected<lldb::TypeSystemSP>
   GetTypeSystemForLanguage(lldb::LanguageType language) override;
 
   lldb_private::CompilerDeclContext FindNamespace(
       lldb_private::ConstString name,
       const lldb_private::CompilerDeclContext &parent_decl_ctx) override;
 
   std::vector<std::unique_ptr<lldb_private::CallEdge>>
   ParseCallEdgesInFunction(UserID func_id) override;

lldb/include/lldb/Symbol/TaggedASTType.h

 
 // For cases in which there are multiple classes of types that are not
 // interchangeable, to allow static type checking.
 template <unsigned int C> class TaggedASTType : public CompilerType {
 public:
   TaggedASTType(const CompilerType &compiler_type)
       : CompilerType(compiler_type) {}
 
-  TaggedASTType(lldb::opaque_compiler_type_t type, TypeSystem *type_system)
+  TaggedASTType(lldb::opaque_compiler_type_t type,
+                lldb::TypeSystemWP type_system)
       : CompilerType(type_system, type) {}
 
   TaggedASTType(const TaggedASTType<C> &tw) : CompilerType(tw) {}
 
   TaggedASTType() : CompilerType() {}
 
   virtual ~TaggedASTType() = default;
 

lldb/include/lldb/Symbol/Type.h

public:
   TypeImpl GetDereferencedType() const;
 
   TypeImpl GetUnqualifiedType() const;
 
   TypeImpl GetCanonicalType() const;
 
   CompilerType GetCompilerType(bool prefer_dynamic);
 
-  TypeSystem *GetTypeSystem(bool prefer_dynamic);
+  CompilerType::TypeSystemSPWrapper GetTypeSystem(bool prefer_dynamic);
 
   bool GetDescription(lldb_private::Stream &strm,
                       lldb::DescriptionLevel description_level);
 
 private:
   bool CheckModule(lldb::ModuleSP &module_sp) const;
   bool CheckExeModule(lldb::ModuleSP &module_sp) const;
   bool CheckModuleCommon(const lldb::ModuleWP &input_module_wp,

lldb/include/lldb/Symbol/TypeSystem.h

 //===-- TypeSystem.h ------------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLDB_SYMBOL_TYPESYSTEM_H
 #define LLDB_SYMBOL_TYPESYSTEM_H
 
 #include <functional>
-#include <map>
 #include <mutex>
 #include <string>
 
 #include "llvm/ADT/APFloat.h"
 #include "llvm/ADT/APSInt.h"
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/SmallBitVector.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/JSON.h"
 
 #include "lldb/Core/PluginInterface.h"
 #include "lldb/Expression/Expression.h"
 #include "lldb/Symbol/CompilerDecl.h"

 ///
 /// Most of the functions in this class should not be called directly but only
 /// called by their respective counterparts in CompilerType, CompilerDecl and
 /// CompilerDeclContext.
 ///
 /// \see lldb_private::CompilerType
 /// \see lldb_private::CompilerDecl
 /// \see lldb_private::CompilerDeclContext
-class TypeSystem : public PluginInterface {
+class TypeSystem : public PluginInterface,
+                   public std::enable_shared_from_this<TypeSystem> {
 public:
   // Constructors and Destructors
   ~TypeSystem() override;
 
   // LLVM RTTI support
   virtual bool isA(const void *ClassID) const = 0;
 
   static lldb::TypeSystemSP CreateInstance(lldb::LanguageType language,
                                            Module *module);
 
   static lldb::TypeSystemSP CreateInstance(lldb::LanguageType language,
                                            Target *target);
 
-  // Free up any resources associated with this TypeSystem.  Done before
-  // removing all the TypeSystems from the TypeSystemMap.
+  /// Free up any resources associated with this TypeSystem.  Done before
+  /// removing all the TypeSystems from the TypeSystemMap.
   virtual void Finalize() {}
  
   virtual DWARFASTParser *GetDWARFParser() { return nullptr; }
   virtual PDBASTParser *GetPDBParser() { return nullptr; }
   virtual npdb::PdbAstBuilder *GetNativePDBParser() { return nullptr; }
 
   virtual SymbolFile *GetSymbolFile() const { return m_sym_file; }
 
   virtual void SetSymbolFile(SymbolFile *sym_file) { m_sym_file = sym_file; }
 
#endif
   // formatters that are discovered on such a type as attributable to the
   // meaningless type itself, instead preferring to use the dynamic type
   virtual bool IsMeaninglessWithoutDynamicResolution(void *type);
 
   virtual llvm::Optional<llvm::json::Value> ReportStatistics();
 
 protected:
   SymbolFile *m_sym_file = nullptr;
 };
 
 class TypeSystemMap {
 public:
   TypeSystemMap();
   ~TypeSystemMap();
 
   // Clear calls Finalize on all the TypeSystems managed by this map, and then
   // empties the map.
   void Clear();
 
   // Iterate through all of the type systems that are created. Return true from
   // callback to keep iterating, false to stop iterating.
-  void ForEach(std::function<bool(TypeSystem *)> const &callback);
+  void ForEach(std::function<bool(lldb::TypeSystemSP)> const &callback);
 
-  llvm::Expected<TypeSystem &>
+  llvm::Expected<lldb::TypeSystemSP>
   GetTypeSystemForLanguage(lldb::LanguageType language, Module *module,
                            bool can_create);
 
-  llvm::Expected<TypeSystem &>
+  llvm::Expected<lldb::TypeSystemSP>
   GetTypeSystemForLanguage(lldb::LanguageType language, Target *target,
                            bool can_create);
 
 protected:
-  typedef std::map<lldb::LanguageType, lldb::TypeSystemSP> collection;
+  typedef llvm::DenseMap<uint16_t, lldb::TypeSystemSP> collection;
   mutable std::mutex m_mutex; ///< A mutex to keep this object happy in
-                              ///multi-threaded environments.
+                              /// multi-threaded environments.
   collection m_map;
   bool m_clear_in_progress = false;
 
 private:
   typedef llvm::function_ref<lldb::TypeSystemSP()> CreateCallback;
   /// Finds the type system for the given language. If no type system could be
-  /// found for a language and a CreateCallback was provided, the value returned
-  /// by the callback will be treated as the TypeSystem for the language.
+  /// found for a language and a CreateCallback was provided, the value
+  /// returned by the callback will be treated as the TypeSystem for the
+  /// language.
   ///
   /// \param language The language for which the type system should be found.
   /// \param create_callback A callback that will be called if no previously
   ///                        created TypeSystem that fits the given language
   ///                        could found. Can be omitted if a non-existent
-  ///                        type system should be treated as an error instead.
+  ///                        type system should be treated as an error
+  ///                        instead.
   /// \return The found type system or an error.
-  llvm::Expected<TypeSystem &> GetTypeSystemForLanguage(
+  llvm::Expected<lldb::TypeSystemSP> GetTypeSystemForLanguage(
       lldb::LanguageType language,
       llvm::Optional<CreateCallback> create_callback = llvm::None);
   };
 
 } // namespace lldb_private
 
 #endif // LLDB_SYMBOL_TYPESYSTEM_H

lldb/include/lldb/Target/Target.h

public:
   lldb::ThreadSP CalculateThread() override;
 
   lldb::StackFrameSP CalculateStackFrame() override;
 
   void CalculateExecutionContext(ExecutionContext &exe_ctx) override;
 
   PathMappingList &GetImageSearchPathList();
 
-  llvm::Expected<TypeSystem &>
+  llvm::Expected<lldb::TypeSystemSP>
   GetScratchTypeSystemForLanguage(lldb::LanguageType language,
                                   bool create_on_demand = true);
 
-  std::vector<TypeSystem *> GetScratchTypeSystems(bool create_on_demand = true);
+  std::vector<lldb::TypeSystemSP>
+  GetScratchTypeSystems(bool create_on_demand = true);
 
   PersistentExpressionState *
   GetPersistentExpressionStateForLanguage(lldb::LanguageType language);
 
   // Creates a UserExpression for the given language, the rest of the
   // parameters have the same meaning as for the UserExpression constructor.
   // Returns a new-ed object which the caller owns.
 

lldb/include/lldb/lldb-enumerations.h

 //===-- lldb-enumerations.h -------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLDB_LLDB_ENUMERATIONS_H
 #define LLDB_LLDB_ENUMERATIONS_H
 
+#include <cstdint>
 #include <type_traits>
 
 #ifndef SWIG
 // Macro to enable bitmask operations on an enum.  Without this, Enum | Enum
 // gets promoted to an int, so you have to say Enum a = Enum(eFoo | eBar).  If
 // you mark Enum with LLDB_MARK_AS_BITMASK_ENUM(Enum), however, you can simply
 // write Enum a = eFoo | eBar.
 // Unfortunately, swig<3.0 doesn't recognise the constexpr keyword, so remove
FLAGS_ENUM(WatchpointEventType){
     eWatchpointEventTypeTypeChanged = (1u << 12)};
 
 /// Programming language type.
 ///
 /// These enumerations use the same language enumerations as the DWARF
 /// specification for ease of use and consistency.
 /// The enum -> string code is in Language.cpp, don't change this
 /// table without updating that code as well.
-enum LanguageType {
+enum LanguageType : uint16_t {
   eLanguageTypeUnknown = 0x0000,        ///< Unknown or invalid language value.
   eLanguageTypeC89 = 0x0001,            ///< ISO C:1989.
   eLanguageTypeC = 0x0002,              ///< Non-standardized C, such as K&R.
   eLanguageTypeAda83 = 0x0003,          ///< ISO Ada:1983.
   eLanguageTypeC_plus_plus = 0x0004,    ///< ISO C++:1998.
   eLanguageTypeCobol74 = 0x0005,        ///< ISO Cobol:1974.
   eLanguageTypeCobol85 = 0x0006,        ///< ISO Cobol:1985.
   eLanguageTypeFortran77 = 0x0007,      ///< ISO Fortran 77.

lldb/include/lldb/lldb-forward.h

 typedef std::weak_ptr<lldb_private::Type> TypeWP;
 typedef std::shared_ptr<lldb_private::TypeCategoryImpl> TypeCategoryImplSP;
 typedef std::shared_ptr<lldb_private::TypeImpl> TypeImplSP;
 typedef std::shared_ptr<lldb_private::TypeMemberFunctionImpl>
     TypeMemberFunctionImplSP;
 typedef std::shared_ptr<lldb_private::TypeEnumMemberImpl> TypeEnumMemberImplSP;
 typedef std::shared_ptr<lldb_private::TypeFilterImpl> TypeFilterImplSP;
 typedef std::shared_ptr<lldb_private::TypeSystem> TypeSystemSP;
+typedef std::weak_ptr<lldb_private::TypeSystem> TypeSystemWP;
 typedef std::shared_ptr<lldb_private::TypeFormatImpl> TypeFormatImplSP;
 typedef std::shared_ptr<lldb_private::TypeNameSpecifierImpl>
     TypeNameSpecifierImplSP;
 typedef std::shared_ptr<lldb_private::TypeSummaryImpl> TypeSummaryImplSP;
 typedef std::shared_ptr<lldb_private::TypeSummaryOptions> TypeSummaryOptionsSP;
 typedef std::shared_ptr<lldb_private::ScriptedSyntheticChildren>
     ScriptedSyntheticChildrenSP;
 typedef std::shared_ptr<lldb_private::UnixSignals> UnixSignalsSP;

lldb/source/API/SBModule.cpp

lldb::SBValue SBModule::FindFirstGlobalVariable(lldb::SBTarget &target,
   if (sb_value_list.IsValid() && sb_value_list.GetSize() > 0)
     return sb_value_list.GetValueAtIndex(0);
   return SBValue();
 }
 
 lldb::SBType SBModule::FindFirstType(const char *name_cstr) {
   LLDB_INSTRUMENT_VA(this, name_cstr);
 
-  SBType sb_type;
   ModuleSP module_sp(GetSP());
-  if (name_cstr && module_sp) {
-    SymbolContext sc;
-    const bool exact_match = false;
-    ConstString name(name_cstr);
+  if (!name_cstr || !module_sp)
+    return {};
 
-    sb_type = SBType(module_sp->FindFirstType(sc, name, exact_match));
+  SBType sb_type = SBType(module_sp->FindFirstType(sc, name, exact_match));
 
-    if (!sb_type.IsValid()) {
-      auto type_system_or_err =
-          module_sp->GetTypeSystemForLanguage(eLanguageTypeC);
-      if (auto err = type_system_or_err.takeError()) {
-        llvm::consumeError(std::move(err));
-        return SBType();
-      }
-      sb_type = SBType(type_system_or_err->GetBuiltinTypeByName(name));
-    }
-  }
-  return sb_type;
+  if (sb_type.IsValid())
+    return sb_type;
+
+  auto type_system_or_err = module_sp->GetTypeSystemForLanguage(eLanguageTypeC);
+    return {};
+
+  if (auto ts = *type_system_or_err)
+    return SBType(ts->GetBuiltinTypeByName(name));
+
+  return {};
 }
 
 lldb::SBType SBModule::GetBasicType(lldb::BasicType type) {
   LLDB_INSTRUMENT_VA(this, type);
 
   ModuleSP module_sp(GetSP());
   if (module_sp) {
     auto type_system_or_err =
         module_sp->GetTypeSystemForLanguage(eLanguageTypeC);
     if (auto err = type_system_or_err.takeError()) {
       llvm::consumeError(std::move(err));
     } else {
-      return SBType(type_system_or_err->GetBasicTypeFromAST(type));
+      if (auto ts = *type_system_or_err)
+        return SBType(ts->GetBasicTypeFromAST(type));              
     }
   }
   return SBType();
 }
 
 lldb::SBTypeList SBModule::FindTypes(const char *type) {
   LLDB_INSTRUMENT_VA(this, type);
 
module_sp->FindTypes(name, exact_match, UINT32_MAX, searched_symbol_files,
                          type_list);
 
     if (type_list.Empty()) {
       auto type_system_or_err =
           module_sp->GetTypeSystemForLanguage(eLanguageTypeC);
       if (auto err = type_system_or_err.takeError()) {
         llvm::consumeError(std::move(err));
       } else {
-        CompilerType compiler_type =
-            type_system_or_err->GetBuiltinTypeByName(name);
-        if (compiler_type)
+        if (auto ts = *type_system_or_err)
+          if (CompilerType compiler_type = ts->GetBuiltinTypeByName(name))
             retval.Append(SBType(compiler_type));
       }
     } else {
       for (size_t idx = 0; idx < type_list.GetSize(); idx++) {
         TypeSP type_sp(type_list.GetTypeAtIndex(idx));
         if (type_sp)
           retval.Append(SBType(type_sp));
       }
     }
   }
   return retval;

lldb/source/API/SBTarget.cpp

for (size_t idx = 0; idx < count; idx++) {
       if (module_sp) {
         TypeSP type_sp(
             module_sp->FindFirstType(sc, const_typename, exact_match));
         if (type_sp)
           return SBType(type_sp);
       }
     }
 
-    // Didn't find the type in the symbols; Try the loaded language runtimes
+    // Didn't find the type in the symbols; Try the loaded language runtimes.
     if (auto process_sp = target_sp->GetProcessSP()) {
       for (auto *runtime : process_sp->GetLanguageRuntimes()) {
         if (auto vendor = runtime->GetDeclVendor()) {
           auto types = vendor->FindTypes(const_typename, /*max_matches*/ 1);
           if (!types.empty())
             return SBType(types.front());
         }
       }
     }
 
-    // No matches, search for basic typename matches
-    for (auto *type_system : target_sp->GetScratchTypeSystems())
-      if (auto type = type_system->GetBuiltinTypeByName(const_typename))
+    // No matches, search for basic typename matches.
+    for (auto type_system_sp : target_sp->GetScratchTypeSystems())
+      if (auto type = type_system_sp->GetBuiltinTypeByName(const_typename))
         return SBType(type);
   }
 
   return SBType();
 }
 
 SBType SBTarget::GetBasicType(lldb::BasicType type) {
   LLDB_INSTRUMENT_VA(this, type);
 
   TargetSP target_sp(GetSP());
   if (target_sp) {
-    for (auto *type_system : target_sp->GetScratchTypeSystems())
-      if (auto compiler_type = type_system->GetBasicTypeFromAST(type))
+    for (auto type_system_sp : target_sp->GetScratchTypeSystems())
+      if (auto compiler_type = type_system_sp->GetBasicTypeFromAST(type))
         return SBType(compiler_type);
   }
   return SBType();
 }
 
 lldb::SBTypeList SBTarget::FindTypes(const char *typename_cstr) {
   LLDB_INSTRUMENT_VA(this, typename_cstr);
 
if (auto process_sp = target_sp->GetProcessSP()) {
           for (auto type : types)
             sb_type_list.Append(SBType(type));
         }
       }
     }
 
     if (sb_type_list.GetSize() == 0) {
       // No matches, search for basic typename matches
-      for (auto *type_system : target_sp->GetScratchTypeSystems())
+      for (auto type_system_sp : target_sp->GetScratchTypeSystems())
         if (auto compiler_type =
-                type_system->GetBuiltinTypeByName(const_typename))
+                type_system_sp->GetBuiltinTypeByName(const_typename))
           sb_type_list.Append(SBType(compiler_type));
     }
   }
   return sb_type_list;
 }
 
 SBValueList SBTarget::FindGlobalVariables(const char *name,
                                           uint32_t max_matches) {

lldb/source/API/SBType.cpp

 
 #include <memory>
 
 using namespace lldb;
 using namespace lldb_private;
 
 SBType::SBType() { LLDB_INSTRUMENT_VA(this); }
 
-SBType::SBType(const CompilerType &type)
-    : m_opaque_sp(new TypeImpl(
-          CompilerType(type.GetTypeSystem(), type.GetOpaqueQualType()))) {}
+SBType::SBType(const CompilerType &type) : m_opaque_sp(new TypeImpl(type)) {}
 
 SBType::SBType(const lldb::TypeSP &type_sp)
     : m_opaque_sp(new TypeImpl(type_sp)) {}
 
 SBType::SBType(const lldb::TypeImplSP &type_impl_sp)
     : m_opaque_sp(type_impl_sp) {}
 
 SBType::SBType(const SBType &rhs) {
if (IsValid())
     return m_opaque_sp->GetCompilerType(false).GetBasicTypeEnumeration();
   return eBasicTypeInvalid;
 }
 
 SBType SBType::GetBasicType(lldb::BasicType basic_type) {
   LLDB_INSTRUMENT_VA(this, basic_type);
 
   if (IsValid() && m_opaque_sp->IsValid())
-    return SBType(
-        m_opaque_sp->GetTypeSystem(false)->GetBasicTypeFromAST(basic_type));
+    if (auto ts = m_opaque_sp->GetTypeSystem(false))
+      return SBType(ts->GetBasicTypeFromAST(basic_type));
   return SBType();
 }
 
 uint32_t SBType::GetNumberOfDirectBaseClasses() {
   LLDB_INSTRUMENT_VA(this);
 
   if (IsValid())
     return m_opaque_sp->GetCompilerType(true).GetNumDirectBaseClasses();

lldb/source/Breakpoint/Watchpoint.cpp

else {
     // If we don't have a known type, then we force it to unsigned int of the
     // right size.
     auto type_system_or_err =
         target.GetScratchTypeSystemForLanguage(eLanguageTypeC);
     if (auto err = type_system_or_err.takeError()) {
       LLDB_LOG_ERROR(GetLog(LLDBLog::Watchpoints), std::move(err),
                      "Failed to set type.");
     } else {
-      m_type = type_system_or_err->GetBuiltinTypeForEncodingAndBitSize(
-          eEncodingUint, 8 * size);
+      if (auto ts = *type_system_or_err)
+        m_type =
+            ts->GetBuiltinTypeForEncodingAndBitSize(eEncodingUint, 8 * size);
+      else
+        LLDB_LOG_ERROR(GetLog(LLDBLog::Watchpoints), std::move(err),
+                       "Failed to set type. Typesystem is no longer live.");
     }
   }
 
   // Set the initial value of the watched variable:
   if (m_target.GetProcessSP()) {
     ExecutionContext exe_ctx;
     m_target.GetProcessSP()->CalculateExecutionContext(exe_ctx);
     CaptureWatchedValue(exe_ctx);

lldb/source/Commands/CommandObjectTarget.cpp

CommandObjectTargetDumpTypesystem(CommandInterpreter &interpreter)
             "Intended to be used for debugging LLDB itself.",
             nullptr, eCommandRequiresTarget) {}
 
   ~CommandObjectTargetDumpTypesystem() override = default;
 
 protected:
   bool DoExecute(Args &command, CommandReturnObject &result) override {
     // Go over every scratch TypeSystem and dump to the command output.
-    for (TypeSystem *ts : GetSelectedTarget().GetScratchTypeSystems())
+    for (lldb::TypeSystemSP ts : GetSelectedTarget().GetScratchTypeSystems())
+      if (ts)
         ts->Dump(result.GetOutputStream().AsRawOstream());
 
     result.SetStatus(eReturnStatusSuccessFinishResult);
     return result.Succeeded();
   }
 };
 
 #pragma mark CommandObjectTargetDump
 

lldb/source/Core/DumpDataExtractor.cpp

for (auto tag : tags) {
     else
       s->PutCString(" <no tag>");
   }
   s->PutCString(")");
 }
 
 static const llvm::fltSemantics &GetFloatSemantics(const TargetSP &target_sp,
                                                    size_t byte_size) {
   if (target_sp) {
-    if (auto type_system_or_err =
-            target_sp->GetScratchTypeSystemForLanguage(eLanguageTypeC))
-      return type_system_or_err->GetFloatTypeSemantics(byte_size);
-    else
+    auto type_system_or_err =
+      target_sp->GetScratchTypeSystemForLanguage(eLanguageTypeC);
+    if (!type_system_or_err)
       llvm::consumeError(type_system_or_err.takeError());
+    else if (auto ts = *type_system_or_err)
+      return ts->GetFloatTypeSemantics(byte_size);
   }
   // No target, just make a reasonable guess
   switch(byte_size) {
     case 2:
       return llvm::APFloat::IEEEhalf();
     case 4:
       return llvm::APFloat::IEEEsingle();
     case 8:

lldb/source/Core/Module.cpp

void Module::SetUUID(const lldb_private::UUID &uuid) {
   if (!m_did_set_uuid) {
     m_uuid = uuid;
     m_did_set_uuid = true;
   } else {
     lldbassert(0 && "Attempting to overwrite the existing module UUID");
   }
 }
 
-llvm::Expected<TypeSystem &>
+llvm::Expected<TypeSystemSP>
 Module::GetTypeSystemForLanguage(LanguageType language) {
   return m_type_system_map.GetTypeSystemForLanguage(language, this, true);
 }
 
 void Module::ForEachTypeSystem(
-    llvm::function_ref<bool(TypeSystem *)> callback) {
+    llvm::function_ref<bool(lldb::TypeSystemSP)> callback) {
   m_type_system_map.ForEach(callback);
 }
 
 void Module::ParseAllDebugSymbols() {
   std::lock_guard<std::recursive_mutex> guard(m_mutex);
   size_t num_comp_units = GetNumCompileUnits();
   if (num_comp_units == 0)
     return;

lldb/source/Core/ValueObjectMemory.cpp

 ValueObjectMemory::ValueObjectMemory(ExecutionContextScope *exe_scope,
                                      ValueObjectManager &manager,
                                      llvm::StringRef name,
                                      const Address &address,
                                      const CompilerType &ast_type)
     : ValueObject(exe_scope, manager), m_address(address), m_type_sp(),
       m_compiler_type(ast_type) {
   // Do not attempt to construct one of these objects with no variable!
-  assert(m_compiler_type.GetTypeSystem());
-  assert(m_compiler_type.GetOpaqueQualType());
+  assert(m_compiler_type.IsValid());
 
   TargetSP target_sp(GetTargetSP());
 
   SetName(ConstString(name));
   m_value.SetCompilerType(m_compiler_type);
   lldb::addr_t load_address = m_address.GetLoadAddress(target_sp.get());
   if (load_address != LLDB_INVALID_ADDRESS) {
     m_value.SetValueType(Value::ValueType::LoadAddress);

lldb/source/Core/ValueObjectRegister.cpp

if (!m_compiler_type.IsValid()) {
     if (auto *target = exe_ctx.GetTargetPtr()) {
       if (auto *exe_module = target->GetExecutableModulePointer()) {
         auto type_system_or_err =
             exe_module->GetTypeSystemForLanguage(eLanguageTypeC);
         if (auto err = type_system_or_err.takeError()) {
           LLDB_LOG_ERROR(GetLog(LLDBLog::Types), std::move(err),
                          "Unable to get CompilerType from TypeSystem");
         } else {
-          m_compiler_type =
-              type_system_or_err->GetBuiltinTypeForEncodingAndBitSize(
-                  m_reg_info.encoding, m_reg_info.byte_size * 8);
+          if (auto ts = *type_system_or_err)
+            m_compiler_type = ts->GetBuiltinTypeForEncodingAndBitSize(
         }
       }
     }
   }
   return m_compiler_type;
 }
 
 ConstString ValueObjectRegister::GetTypeName() {

lldb/source/DataFormatters/VectorType.cpp

 #include "lldb/Utility/Log.h"
 
 using namespace lldb;
 using namespace lldb_private;
 using namespace lldb_private::formatters;
 
 static CompilerType GetCompilerTypeForFormat(lldb::Format format,
                                              CompilerType element_type,
-                                             TypeSystem *type_system) {
+                                             TypeSystemSP type_system) {
   lldbassert(type_system && "type_system needs to be not NULL");
+  if (!type_system)
+    return {};
 
   switch (format) {
   case lldb::eFormatAddressInfo:
   case lldb::eFormatPointer:
     return type_system->GetBuiltinTypeForEncodingAndBitSize(
         eEncodingUint, 8 * type_system->GetPointerByteSize());
 
   case lldb::eFormatBoolean:
lldb::ValueObjectSP GetChildAtIndex(size_t idx) override {
     return child_sp;
   }
 
   bool Update() override {
     m_parent_format = m_backend.GetFormat();
     CompilerType parent_type(m_backend.GetCompilerType());
     CompilerType element_type;
     parent_type.IsVectorType(&element_type);
-    m_child_type = ::GetCompilerTypeForFormat(m_parent_format, element_type,
-                                              parent_type.GetTypeSystem());
+    m_child_type = ::GetCompilerTypeForFormat(
+        m_parent_format, element_type,
+        parent_type.GetTypeSystem().GetSharedPointer());
     m_num_children = ::CalculateNumChildren(parent_type, m_child_type);
     m_item_format = GetItemFormatForFormat(m_parent_format, m_child_type);
     return false;
   }
 
   bool MightHaveChildren() override { return true; }
 
   size_t GetIndexOfChildWithName(ConstString name) override {

lldb/source/Expression/Materializer.cpp

void Dematerialize(lldb::StackFrameSP &frame_sp, IRMemoryMap &map,
 
     if (auto error = type_system_or_err.takeError()) {
       err.SetErrorStringWithFormat("Couldn't dematerialize a result variable: "
                                    "couldn't get the corresponding type "
                                    "system: %s",
                                    llvm::toString(std::move(error)).c_str());
       return;
     }
+    auto ts = *type_system_or_err;
+    if (!ts) {
+      err.SetErrorStringWithFormat("Couldn't dematerialize a result variable: "
+                                   "couldn't corresponding type system is "
+                                   "no longer live.");
+      return;
+    }
     PersistentExpressionState *persistent_state =
-        type_system_or_err->GetPersistentExpressionState();
+        ts->GetPersistentExpressionState();
 
     if (!persistent_state) {
       err.SetErrorString("Couldn't dematerialize a result variable: "
                          "corresponding type system doesn't handle persistent "
                          "variables");
       return;
     }
 

lldb/source/Plugins/ABI/PowerPC/ABISysV_ppc64.cpp

if (m_type.IsHomogeneousAggregate(&elem_type)) {
         m_dst_offs += *elem_size;
       }
       return BuildValueObject();
     }
 
     // case 3: get from GPRs
 
     // first, check if this is a packed struct or not
-    TypeSystemClang *ast =
-        llvm::dyn_cast<TypeSystemClang>(m_type.GetTypeSystem());
+    auto ast = m_type.GetTypeSystem().dyn_cast_or_null<TypeSystemClang>();
     if (ast) {
       clang::RecordDecl *record_decl = TypeSystemClang::GetAsRecordDecl(m_type);
 
       if (record_decl) {
         auto attrs = record_decl->attrs();
         for (const auto &attr : attrs) {
           if (attr->getKind() == clang::attr::Packed) {
             m_packed = true;

lldb/source/Plugins/ABI/X86/ABISysV_x86_64.cpp

ValueObjectSP ABISysV_x86_64::GetReturnValueObjectImpl(
   llvm::Optional<uint64_t> bit_width = return_compiler_type.GetBitSize(&thread);
   if (!bit_width)
     return return_valobj_sp;
   if (return_compiler_type.IsAggregateType()) {
     Target *target = exe_ctx.GetTargetPtr();
     bool is_memory = true;
     std::vector<uint32_t> aggregate_field_offsets;
     std::vector<CompilerType> aggregate_compiler_types;
-    if (return_compiler_type.GetTypeSystem()->CanPassInRegisters(
-          return_compiler_type) &&
+    auto ts = return_compiler_type.GetTypeSystem();
+    if (ts && ts->CanPassInRegisters(return_compiler_type) &&
         *bit_width <= 128 &&
-      FlattenAggregateType(thread, exe_ctx, return_compiler_type,
-                          0, aggregate_field_offsets,
+        FlattenAggregateType(thread, exe_ctx, return_compiler_type, 0,
+                             aggregate_field_offsets,
                              aggregate_compiler_types)) {
       ByteOrder byte_order = target->GetArchitecture().GetByteOrder();
       WritableDataBufferSP data_sp(new DataBufferHeap(16, 0));
       DataExtractor return_ext(data_sp, byte_order,
                                target->GetArchitecture().GetAddressByteSize());
 
       const RegisterInfo *rax_info =
           reg_ctx_sp->GetRegisterInfoByName("rax", 0);
       const RegisterInfo *rdx_info =

lldb/source/Plugins/ExpressionParser/Clang/ClangASTImporter.cpp

 
 using namespace lldb_private;
 using namespace clang;
 
 CompilerType ClangASTImporter::CopyType(TypeSystemClang &dst_ast,
                                         const CompilerType &src_type) {
   clang::ASTContext &dst_clang_ast = dst_ast.getASTContext();
 
-  TypeSystemClang *src_ast =
-      llvm::dyn_cast_or_null<TypeSystemClang>(src_type.GetTypeSystem());
+  auto src_ast = src_type.GetTypeSystem().dyn_cast_or_null<TypeSystemClang>();
   if (!src_ast)
     return CompilerType();
 
   clang::ASTContext &src_clang_ast = src_ast->getASTContext();
 
   clang::QualType src_qual_type = ClangUtil::GetQualType(src_type);
 
   ImporterDelegateSP delegate_sp(GetDelegate(&dst_clang_ast, &src_clang_ast));
   if (!delegate_sp)
     return CompilerType();
 
   ASTImporterDelegate::CxxModuleScope std_scope(*delegate_sp, &dst_clang_ast);
 
   llvm::Expected<QualType> ret_or_error = delegate_sp->Import(src_qual_type);
   if (!ret_or_error) {
     Log *log = GetLog(LLDBLog::Expressions);
     LLDB_LOG_ERROR(log, ret_or_error.takeError(),
         "Couldn't import type: {0}");
     return CompilerType();
   }
 
   lldb::opaque_compiler_type_t dst_clang_type = ret_or_error->getAsOpaquePtr();
 
   if (dst_clang_type)
-    return CompilerType(&dst_ast, dst_clang_type);
+    return CompilerType(dst_ast.weak_from_this(), dst_clang_type);
   return CompilerType();
 }
 
 clang::Decl *ClangASTImporter::CopyDecl(clang::ASTContext *dst_ast,
                                         clang::Decl *decl) {
   ImporterDelegateSP delegate_sp;
 
   clang::ASTContext *src_ast = &decl->getASTContext();
public:
   }
 };
 } // namespace
 
 CompilerType ClangASTImporter::DeportType(TypeSystemClang &dst,
                                           const CompilerType &src_type) {
   Log *log = GetLog(LLDBLog::Expressions);
 
-  TypeSystemClang *src_ctxt =
-      llvm::cast<TypeSystemClang>(src_type.GetTypeSystem());
+  auto src_ctxt = src_type.GetTypeSystem().dyn_cast_or_null<TypeSystemClang>();
+  if (!src_ctxt)
+    return {};
 
   LLDB_LOG(log,
            "    [ClangASTImporter] DeportType called on ({0}Type*){1} "
            "from (ASTContext*){2} to (ASTContext*){3}",
            src_type.GetTypeName(), src_type.GetOpaqueQualType(),
            &src_ctxt->getASTContext(), &dst.getASTContext());
 
   DeclContextOverride decl_context_override;

lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.cpp

clang::Decl *ClangASTSource::CopyDecl(Decl *src_decl) {
   return m_ast_importer_sp->CopyDecl(m_ast_context, src_decl);
 }
 
 ClangASTImporter::DeclOrigin ClangASTSource::GetDeclOrigin(const clang::Decl *decl) {
   return m_ast_importer_sp->GetDeclOrigin(decl);
 }
 
 CompilerType ClangASTSource::GuardedCopyType(const CompilerType &src_type) {
-  TypeSystemClang *src_ast =
-      llvm::dyn_cast_or_null<TypeSystemClang>(src_type.GetTypeSystem());
-  if (src_ast == nullptr)
-    return CompilerType();
+  auto ts = src_type.GetTypeSystem();
+  auto src_ast = ts.dyn_cast_or_null<TypeSystemClang>();
+  if (!src_ast)
+    return {};
 
   QualType copied_qual_type = ClangUtil::GetQualType(
       m_ast_importer_sp->CopyType(*m_clang_ast_context, src_type));
 
   if (copied_qual_type.getAsOpaquePtr() &&
       copied_qual_type->getCanonicalTypeInternal().isNull())
     // this shouldn't happen, but we're hardening because the AST importer
     // seems to be generating bad types on occasion.
-    return CompilerType();
+    return {};
 
   return m_clang_ast_context->GetType(copied_qual_type);
 }
 
 std::shared_ptr<ClangModulesDeclVendor>
 ClangASTSource::GetClangModulesDeclVendor() {
   auto persistent_vars = llvm::cast<ClangPersistentVariables>(
       m_target->GetPersistentExpressionStateForLanguage(lldb::eLanguageTypeC));
   return persistent_vars->GetClangModulesDeclVendor();
 }

lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp

ClangExpressionDeclMap::TargetInfo ClangExpressionDeclMap::GetTargetInfo() {
 
   return ret;
 }
 
 TypeFromUser ClangExpressionDeclMap::DeportType(TypeSystemClang &target,
                                                 TypeSystemClang &source,
                                                 TypeFromParser parser_type) {
   assert(&target == GetScratchContext(*m_target));
-  assert((TypeSystem *)&source == parser_type.GetTypeSystem());
+  assert((TypeSystem *)&source ==
+         parser_type.GetTypeSystem().GetSharedPointer().get());
   assert(&source.getASTContext() == m_ast_context);
 
   return TypeFromUser(m_ast_importer_sp->DeportType(target, parser_type));
 }
 
 bool ClangExpressionDeclMap::AddPersistentVariable(const NamedDecl *decl,
                                                    ConstString name,
                                                    TypeFromParser parser_type,
                                                    bool is_result,
                                                    bool is_lvalue) {
   assert(m_parser_vars.get());
-
-  TypeSystemClang *ast =
-      llvm::dyn_cast_or_null<TypeSystemClang>(parser_type.GetTypeSystem());
+  auto ast = parser_type.GetTypeSystem().dyn_cast_or_null<TypeSystemClang>();
   if (ast == nullptr)
     return false;
 
   // Check if we already declared a persistent variable with the same name.
   if (lldb::ExpressionVariableSP conflicting_var =
           m_parser_vars->m_persistent_vars->GetVariable(name)) {
     std::string msg = llvm::formatv("redefinition of persistent variable '{0}'",
                                     name).str();
if (auto capturedThis = GetCapturedThisValueObject(frame)) {
       AddContextClassType(context, pointee_type);
       return;
     }
 
     clang::CXXRecordDecl *class_decl = method_decl->getParent();
 
     QualType class_qual_type(class_decl->getTypeForDecl(), 0);
 
-    TypeFromUser class_user_type(class_qual_type.getAsOpaquePtr(),
-                                 function_decl_ctx.GetTypeSystem());
+    TypeFromUser class_user_type(
+        class_qual_type.getAsOpaquePtr(),
+        function_decl_ctx.GetTypeSystem()->weak_from_this());
 
     LLDB_LOG(log, "  CEDM::FEVD Adding type for $__lldb_class: {0}",
              class_qual_type.getAsString());
 
     AddContextClassType(context, class_user_type);
     return;
   }
 
if (!self_interface)
       return;
 
     const clang::Type *interface_type = self_interface->getTypeForDecl();
 
     if (!interface_type)
       return; // This is unlikely, but we have seen crashes where this
               // occurred
 
-    TypeFromUser class_user_type(QualType(interface_type, 0).getAsOpaquePtr(),
-                                 function_decl_ctx.GetTypeSystem());
+    TypeFromUser class_user_type(
+        QualType(interface_type, 0).getAsOpaquePtr(),
+        function_decl_ctx.GetTypeSystem()->weak_from_this());
 
     LLDB_LOG(log, "  FEVD[{0}] Adding type for $__lldb_objc_class: {1}",
              ClangUtil::ToString(interface_type));
 
     AddOneType(context, class_user_type);
     return;
   }
   // This branch will get hit if we are executing code in the context of
bool ClangExpressionDeclMap::GetVariableValue(VariableSP &var,
 
   CompilerType var_clang_type = var_type->GetFullCompilerType();
 
   if (!var_clang_type) {
     LLDB_LOG(log, "Skipped a definition because it has no Clang type");
     return false;
   }
 
-  TypeSystemClang *clang_ast = llvm::dyn_cast_or_null<TypeSystemClang>(
-      var_type->GetForwardCompilerType().GetTypeSystem());
+  auto ts = var_type->GetForwardCompilerType().GetTypeSystem();
+  auto clang_ast = ts.dyn_cast_or_null<TypeSystemClang>();
 
   if (!clang_ast) {
     LLDB_LOG(log, "Skipped a definition because it has no Clang AST");
     return false;
   }
 
   DWARFExpressionList &var_location_list = var->LocationExpressionList();
 
void ClangExpressionDeclMap::AddOneVariable(
   assert(valobj);
 
   Log *log = GetLog(LLDBLog::Expressions);
 
   Value var_location = valobj->GetValue();
 
   TypeFromUser user_type = valobj->GetCompilerType();
 
-  TypeSystemClang *clang_ast =
-      llvm::dyn_cast_or_null<TypeSystemClang>(user_type.GetTypeSystem());
+  auto clang_ast =
+      user_type.GetTypeSystem().dyn_cast_or_null<TypeSystemClang>();
 
   if (!clang_ast) {
     LLDB_LOG(log, "Skipped a definition because it has no Clang AST");
     return;
   }
 
   TypeFromParser parser_type = GuardedCopyType(user_type);
 

lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.h

private:
   std::unique_ptr<clang::CompilerInstance>
       m_compiler; ///< The Clang compiler used to parse expressions into IR
   std::unique_ptr<clang::CodeGenerator>
       m_code_generator; ///< The Clang object that generates IR
 
   class LLDBPreprocessorCallbacks;
   LLDBPreprocessorCallbacks *m_pp_callbacks; ///< Called when the preprocessor
                                              ///encounters module imports
-  std::unique_ptr<TypeSystemClang> m_ast_context;
+  std::shared_ptr<TypeSystemClang> m_ast_context;
 
   std::vector<std::string> m_include_directories;
   /// File name used for the user expression.
   std::string m_filename;
 };
 }
 
 #endif // LLDB_SOURCE_PLUGINS_EXPRESSIONPARSER_CLANG_CLANGEXPRESSIONPARSER_H

lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp

ClangExpressionParser::ClangExpressionParser(
   auto &PP = m_compiler->getPreprocessor();
   auto &builtin_context = PP.getBuiltinInfo();
   builtin_context.initializeBuiltins(PP.getIdentifierTable(),
                                      m_compiler->getLangOpts());
 
   m_compiler->createASTContext();
   clang::ASTContext &ast_context = m_compiler->getASTContext();
 
-  m_ast_context = std::make_unique<TypeSystemClang>(
+  m_ast_context = std::make_shared<TypeSystemClang>(
       "Expression ASTContext for '" + m_filename + "'", ast_context);
 
   std::string module_name("$__lldb_module");
 
   m_llvm_context = std::make_unique<LLVMContext>();
   m_code_generator.reset(CreateLLVMCodeGen(
       m_compiler->getDiagnostics(), module_name,
       &m_compiler->getVirtualFileSystem(), m_compiler->getHeaderSearchOpts(),

lldb/source/Plugins/ExpressionParser/Clang/ClangModulesDeclVendor.cpp

private:
 
   typedef std::vector<ConstString> ImportedModule;
   typedef std::map<ImportedModule, clang::Module *> ImportedModuleMap;
   typedef llvm::DenseSet<ModuleID> ImportedModuleSet;
   ImportedModuleMap m_imported_modules;
   ImportedModuleSet m_user_imported_modules;
   // We assume that every ASTContext has an TypeSystemClang, so we also store
   // a custom TypeSystemClang for our internal ASTContext.
-  std::unique_ptr<TypeSystemClang> m_ast_context;
+  std::shared_ptr<TypeSystemClang> m_ast_context;
 };
 } // anonymous namespace
 
 StoringDiagnosticConsumer::StoringDiagnosticConsumer() {
   m_log = GetLog(LLDBLog::Expressions);
 
   clang::DiagnosticOptions *m_options = new clang::DiagnosticOptions();
   m_os = std::make_shared<llvm::raw_string_ostream>(m_output);
ClangModulesDeclVendorImpl::ClangModulesDeclVendorImpl(
     std::unique_ptr<clang::Parser> parser)
     : m_diagnostics_engine(std::move(diagnostics_engine)),
       m_compiler_invocation(std::move(compiler_invocation)),
       m_compiler_instance(std::move(compiler_instance)),
       m_parser(std::move(parser)) {
 
   // Initialize our TypeSystemClang.
   m_ast_context =
-      std::make_unique<TypeSystemClang>("ClangModulesDeclVendor ASTContext",
+      std::make_shared<TypeSystemClang>("ClangModulesDeclVendor ASTContext",
                                         m_compiler_instance->getASTContext());
 }
 
 void ClangModulesDeclVendorImpl::ReportModuleExportsHelper(
     ExportedModuleSet &exports, clang::Module *module) {
   if (exports.count(reinterpret_cast<ClangModulesDeclVendor::ModuleID>(module)))
     return;
 

lldb/source/Plugins/ExpressionParser/Clang/ClangPersistentVariables.h

private:
   uint32_t m_next_user_file_id = 0;
   // The counter used by GetNextPersistentVariableName
   uint32_t m_next_persistent_variable_id = 0;
 
   struct PersistentDecl {
     /// The persistent decl.
     clang::NamedDecl *m_decl = nullptr;
     /// The TypeSystemClang for the ASTContext of m_decl.
-    TypeSystemClang *m_context = nullptr;
+    lldb::TypeSystemWP m_context;
   };
 
   typedef llvm::DenseMap<const char *, PersistentDecl> PersistentDeclMap;
   PersistentDeclMap
       m_persistent_decls; ///< Persistent entities declared by the user.
 
   ClangModulesDeclVendor::ModuleVector
       m_hand_loaded_clang_modules; ///< These are Clang modules we hand-loaded;

lldb/source/Plugins/ExpressionParser/Clang/ClangPersistentVariables.cpp

if (clang::TypeDecl *tdecl = llvm::dyn_cast<clang::TypeDecl>(p.m_decl)) {
     return CompilerType(p.m_context, t);
   }
   return llvm::None;
 }
 
 void ClangPersistentVariables::RegisterPersistentDecl(ConstString name,
                                                       clang::NamedDecl *decl,
                                                       TypeSystemClang *ctx) {
-  PersistentDecl p = {decl, ctx};
+  PersistentDecl p = {decl, ctx->weak_from_this()};
   m_persistent_decls.insert(std::make_pair(name.GetCString(), p));
 
   if (clang::EnumDecl *enum_decl = llvm::dyn_cast<clang::EnumDecl>(decl)) {
     for (clang::EnumConstantDecl *enumerator_decl : enum_decl->enumerators()) {
-      p = {enumerator_decl, ctx};
+      p = {enumerator_decl, ctx->weak_from_this()};
       m_persistent_decls.insert(std::make_pair(
           ConstString(enumerator_decl->getNameAsString()).GetCString(), p));
     }
   }
 }
 
 clang::NamedDecl *
 ClangPersistentVariables::GetPersistentDecl(ConstString name) {

lldb/source/Plugins/ExpressionParser/Clang/ClangUtil.cpp

 using namespace clang;
 using namespace lldb_private;
 
 bool ClangUtil::IsClangType(const CompilerType &ct) {
   // Invalid types are never Clang types.
   if (!ct)
     return false;
 
-  if (llvm::dyn_cast_or_null<TypeSystemClang>(ct.GetTypeSystem()) == nullptr)
+  if (!ct.GetTypeSystem().dyn_cast_or_null<TypeSystemClang>())
     return false;
 
   if (!ct.GetOpaqueQualType())
     return false;
 
   return true;
 }
 

lldb/source/Plugins/ExpressionParser/Clang/NameSearchContext.cpp

 using namespace lldb_private;
 
 clang::NamedDecl *NameSearchContext::AddVarDecl(const CompilerType &type) {
   assert(type && "Type for variable must be valid!");
 
   if (!type.IsValid())
     return nullptr;
 
-  TypeSystemClang *lldb_ast =
-      llvm::dyn_cast<TypeSystemClang>(type.GetTypeSystem());
+  auto lldb_ast = type.GetTypeSystem().dyn_cast_or_null<TypeSystemClang>();
   if (!lldb_ast)
     return nullptr;
 
   IdentifierInfo *ii = m_decl_name.getAsIdentifierInfo();
 
   clang::ASTContext &ast = lldb_ast->getASTContext();
 
   clang::NamedDecl *Decl = VarDecl::Create(
clang::NamedDecl *NameSearchContext::AddFunDecl(const CompilerType &type,
   assert(type && "Type for variable must be valid!");
 
   if (!type.IsValid())
     return nullptr;
 
   if (m_function_types.count(type))
     return nullptr;
 
-  TypeSystemClang *lldb_ast =
-      llvm::dyn_cast<TypeSystemClang>(type.GetTypeSystem());
+  auto lldb_ast = type.GetTypeSystem().dyn_cast_or_null<TypeSystemClang>();
   if (!lldb_ast)
     return nullptr;
 
   m_function_types.insert(type);
 
   QualType qual_type(ClangUtil::GetQualType(type));
 
   clang::ASTContext &ast = lldb_ast->getASTContext();

lldb/source/Plugins/Language/CPlusPlus/BlockPointer.cpp

BlockPointerSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
     auto type_system_or_err = target_sp->GetScratchTypeSystemForLanguage(
         lldb::eLanguageTypeC_plus_plus);
     if (auto err = type_system_or_err.takeError()) {
       LLDB_LOG_ERROR(GetLog(LLDBLog::DataFormatters), std::move(err),
                      "Failed to get scratch TypeSystemClang");
       return;
     }
 
-    TypeSystemClang *clang_ast_context =
-        llvm::cast<TypeSystemClang>(block_pointer_type.GetTypeSystem());
+    auto ts = block_pointer_type.GetTypeSystem();
+    auto clang_ast_context = ts.dyn_cast_or_null<TypeSystemClang>();
+    if (!clang_ast_context)
+      return;
 
     std::shared_ptr<ClangASTImporter> clang_ast_importer;
     auto *state = target_sp->GetPersistentExpressionStateForLanguage(
         lldb::eLanguageTypeC_plus_plus);
     if (state) {
       auto *persistent_vars = llvm::cast<ClangPersistentVariables>(state);
       clang_ast_importer = persistent_vars->GetClangASTImporter();
     }

lldb/source/Plugins/Language/CPlusPlus/Coroutines.cpp

bool lldb_private::formatters::StdlibCoroutineHandleSyntheticFrontEnd::
   ValueObjectSP valobj_sp = m_backend.GetSP();
   if (!valobj_sp)
     return false;
 
   ValueObjectSP ptr_sp(GetCoroFramePtrFromHandle(m_backend));
   if (!ptr_sp)
     return false;
 
-  TypeSystemClang *ast_ctx = llvm::dyn_cast_or_null<TypeSystemClang>(
-      valobj_sp->GetCompilerType().GetTypeSystem());
+  auto ts = valobj_sp->GetCompilerType().GetTypeSystem();
+  auto ast_ctx = ts.dyn_cast_or_null<TypeSystemClang>();
   if (!ast_ctx)
     return false;
 
   CompilerType promise_type(
       valobj_sp->GetCompilerType().GetTypeTemplateArgument(0));
   if (!promise_type)
     return false;
   CompilerType coro_frame_type = GetCoroutineFrameType(*ast_ctx, promise_type);

lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp

if (m_pair_ptr) {
       if (!pair_type) {
         m_pair_ptr = nullptr;
         return false;
       }
 
       auto addr(m_pair_ptr->GetValueAsUnsigned(LLDB_INVALID_ADDRESS));
       m_pair_ptr = nullptr;
       if (addr && addr != LLDB_INVALID_ADDRESS) {
-        TypeSystemClang *ast_ctx =
-            llvm::dyn_cast_or_null<TypeSystemClang>(pair_type.GetTypeSystem());
+        auto ts = pair_type.GetTypeSystem();
+        auto ast_ctx = ts.dyn_cast_or_null<TypeSystemClang>();
         if (!ast_ctx)
           return false;
 
         // Mimick layout of std::__tree_iterator::__ptr_ and read it in
         // from process memory.
         //
         // The following shows the contiguous block of memory:
         //
if (m_iter_ptr) {
     }
 
     uint64_t addr = m_iter_ptr->GetValueAsUnsigned(LLDB_INVALID_ADDRESS);
     m_iter_ptr = nullptr;
 
     if (addr == 0 || addr == LLDB_INVALID_ADDRESS)
       return false;
 
-    TypeSystemClang *ast_ctx =
-        llvm::dyn_cast_or_null<TypeSystemClang>(pair_type.GetTypeSystem());
+    auto ts = pair_type.GetTypeSystem();
+    auto ast_ctx = ts.dyn_cast_or_null<TypeSystemClang>();
     if (!ast_ctx)
       return false;
 
     // Mimick layout of std::__hash_iterator::__node_ and read it in
     // from process memory.
     //
     // The following shows the contiguous block of memory:
     //

lldb/source/Plugins/Language/CPlusPlus/LibCxxMap.cpp

size_t lldb_private::formatters::LibcxxStdMapSyntheticFrontEnd::
   return m_count;
 }
 
 bool lldb_private::formatters::LibcxxStdMapSyntheticFrontEnd::GetDataType() {
   static ConstString g_value_("__value_");
   static ConstString g_tree_("__tree_");
   static ConstString g_pair3("__pair3_");
 
-  if (m_element_type.GetOpaqueQualType() && m_element_type.GetTypeSystem())
+  if (m_element_type.IsValid())
     return true;
   m_element_type.Clear();
   ValueObjectSP deref;
   Status error;
   deref = m_root_node->Dereference(error);
   if (!deref || error.Fail())
     return false;
   deref = deref->GetChildMemberWithName(g_value_, true);
void lldb_private::formatters::LibcxxStdMapSyntheticFrontEnd::GetValueOffset(
   if (!node)
     return;
   CompilerType node_type(node->GetCompilerType());
   uint64_t bit_offset;
   if (node_type.GetIndexOfFieldWithName("__value_", nullptr, &bit_offset) !=
       UINT32_MAX) {
     m_skip_size = bit_offset / 8u;
   } else {
-    TypeSystemClang *ast_ctx =
-        llvm::dyn_cast_or_null<TypeSystemClang>(node_type.GetTypeSystem());
+    auto ast_ctx = node_type.GetTypeSystem().dyn_cast_or_null<TypeSystemClang>();
     if (!ast_ctx)
       return;
     CompilerType tree_node_type = ast_ctx->CreateStructForIdentifier(
         ConstString(),
         {{"ptr0", ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
          {"ptr1", ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
          {"ptr2", ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
          {"cw", ast_ctx->GetBasicType(lldb::eBasicTypeBool)},

lldb/source/Plugins/Language/ObjC/CoreMedia.cpp

 using namespace lldb_private::formatters;
 
 bool lldb_private::formatters::CMTimeSummaryProvider(
     ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) {
   CompilerType type = valobj.GetCompilerType();
   if (!type.IsValid())
     return false;
 
-  TypeSystem *type_system = type.GetTypeSystem();
+  auto type_system = type.GetTypeSystem();
+  if (!type_system)
+    return false;
   // fetch children by offset to compensate for potential lack of debug info
   auto int64_ty =
       type_system->GetBuiltinTypeForEncodingAndBitSize(eEncodingSint, 64);
   auto int32_ty =
       type_system->GetBuiltinTypeForEncodingAndBitSize(eEncodingSint, 32);
 
   auto value_sp(valobj.GetSyntheticChildAtOffset(0, int64_ty, true));
   auto timescale_sp(valobj.GetSyntheticChildAtOffset(8, int32_ty, true));

lldb/source/Plugins/Language/ObjC/NSArray.cpp

 lldb_private::formatters::NSArrayMSyntheticFrontEndBase::
     NSArrayMSyntheticFrontEndBase(lldb::ValueObjectSP valobj_sp)
     : SyntheticChildrenFrontEnd(*valobj_sp), m_exe_ctx_ref(), m_id_type() {
   if (valobj_sp) {
     auto *clang_ast_context = ScratchTypeSystemClang::GetForTarget(
         *valobj_sp->GetExecutionContextRef().GetTargetSP());
     if (clang_ast_context)
       m_id_type = CompilerType(
-          clang_ast_context,
+          clang_ast_context->weak_from_this(),
           clang_ast_context->getASTContext().ObjCBuiltinIdTy.getAsOpaquePtr());
     if (valobj_sp->GetProcessSP())
       m_ptr_size = valobj_sp->GetProcessSP()->GetAddressByteSize();
   }
 }
 
 template <typename D32, typename D64>
 lldb_private::formatters::

lldb/source/Plugins/Language/ObjC/NSIndexPath.cpp

public:
 
   lldb::ValueObjectSP GetChildAtIndex(size_t idx) override {
     return m_impl.GetIndexAtIndex(idx, m_uint_star_type);
   }
 
   bool Update() override {
     m_impl.Clear();
 
-    TypeSystem *type_system = m_backend.GetCompilerType().GetTypeSystem();
+    auto type_system = m_backend.GetCompilerType().GetTypeSystem();
     if (!type_system)
       return false;
 
     TypeSystemClang *ast = ScratchTypeSystemClang::GetForTarget(
         *m_backend.GetExecutionContextRef().GetTargetSP());
     if (!ast)
       return false;
 

lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCDeclVendor.h

public:
 
   friend class AppleObjCExternalASTSource;
 
 private:
   clang::ObjCInterfaceDecl *GetDeclForISA(ObjCLanguageRuntime::ObjCISA isa);
   bool FinishDecl(clang::ObjCInterfaceDecl *decl);
 
   ObjCLanguageRuntime &m_runtime;
-  TypeSystemClang m_ast_ctx;
+  std::shared_ptr<TypeSystemClang> m_ast_ctx;
   ObjCLanguageRuntime::EncodingToTypeSP m_type_realizer_sp;
   AppleObjCExternalASTSource *m_external_source;
 
   typedef llvm::DenseMap<ObjCLanguageRuntime::ObjCISA,
                          clang::ObjCInterfaceDecl *>
       ISAToInterfaceMap;
 
   ISAToInterfaceMap m_isa_to_interface;
 };
 
 } // namespace lldb_private
 
 #endif // LLDB_SOURCE_PLUGINS_LANGUAGERUNTIME_OBJC_APPLEOBJCRUNTIME_APPLEOBJCDECLVENDOR_H

lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCDeclVendor.cpp

bool layoutRecordType(
           &BaseOffsets,
       llvm::DenseMap<const clang::CXXRecordDecl *, clang::CharUnits>
           &VirtualBaseOffsets) override {
     return false;
   }
 
   void StartTranslationUnit(clang::ASTConsumer *Consumer) override {
     clang::TranslationUnitDecl *translation_unit_decl =
-        m_decl_vendor.m_ast_ctx.getASTContext().getTranslationUnitDecl();
+        m_decl_vendor.m_ast_ctx->getASTContext().getTranslationUnitDecl();
     translation_unit_decl->setHasExternalVisibleStorage();
     translation_unit_decl->setHasExternalLexicalStorage();
   }
 
 private:
   AppleObjCDeclVendor &m_decl_vendor;
 };
 
 AppleObjCDeclVendor::AppleObjCDeclVendor(ObjCLanguageRuntime &runtime)
     : ClangDeclVendor(eAppleObjCDeclVendor), m_runtime(runtime),
-      m_ast_ctx(
-          "AppleObjCDeclVendor AST",
-          runtime.GetProcess()->GetTarget().GetArchitecture().GetTriple()),
       m_type_realizer_sp(m_runtime.GetEncodingToType()) {
+  m_ast_ctx = std::make_shared<TypeSystemClang>(
+      "AppleObjCDeclVendor AST",
+      runtime.GetProcess()->GetTarget().GetArchitecture().GetTriple());
   m_external_source = new AppleObjCExternalASTSource(*this);
   llvm::IntrusiveRefCntPtr<clang::ExternalASTSource> external_source_owning_ptr(
       m_external_source);
-  m_ast_ctx.getASTContext().setExternalSource(external_source_owning_ptr);
+  m_ast_ctx->getASTContext().setExternalSource(external_source_owning_ptr);
 }
 
 clang::ObjCInterfaceDecl *
 AppleObjCDeclVendor::GetDeclForISA(ObjCLanguageRuntime::ObjCISA isa) {
   ISAToInterfaceMap::const_iterator iter = m_isa_to_interface.find(isa);
 
   if (iter != m_isa_to_interface.end())
     return iter->second;
 
-  clang::ASTContext &ast_ctx = m_ast_ctx.getASTContext();
+  clang::ASTContext &ast_ctx = m_ast_ctx->getASTContext();
 
   ObjCLanguageRuntime::ClassDescriptorSP descriptor =
       m_runtime.GetClassDescriptorFromISA(isa);
 
   if (!descriptor)
     return nullptr;
 
   ConstString name(descriptor->GetClassName());
 
   clang::IdentifierInfo &identifier_info =
       ast_ctx.Idents.get(name.GetStringRef());
 
   clang::ObjCInterfaceDecl *new_iface_decl = clang::ObjCInterfaceDecl::Create(
       ast_ctx, ast_ctx.getTranslationUnitDecl(), clang::SourceLocation(),
       &identifier_info, nullptr, nullptr);
 
   ClangASTMetadata meta_data;
   meta_data.SetISAPtr(isa);
-  m_ast_ctx.SetMetadata(new_iface_decl, meta_data);
+  m_ast_ctx->SetMetadata(new_iface_decl, meta_data);
 
   new_iface_decl->setHasExternalVisibleStorage();
   new_iface_decl->setHasExternalLexicalStorage();
 
   ast_ctx.getTranslationUnitDecl()->addDecl(new_iface_decl);
 
   m_isa_to_interface[isa] = new_iface_decl;
 
private:
   TypeVector m_type_vector;
   bool m_is_valid = false;
 };
 
 bool AppleObjCDeclVendor::FinishDecl(clang::ObjCInterfaceDecl *interface_decl) {
   Log *log(
       GetLog(LLDBLog::Expressions)); // FIXME - a more appropriate log channel?
 
-  ClangASTMetadata *metadata = m_ast_ctx.GetMetadata(interface_decl);
+  ClangASTMetadata *metadata = m_ast_ctx->GetMetadata(interface_decl);
   ObjCLanguageRuntime::ObjCISA objc_isa = 0;
   if (metadata)
     objc_isa = metadata->GetISAPtr();
 
   if (!objc_isa)
     return false;
 
   if (!interface_decl->hasExternalVisibleStorage())
bool AppleObjCDeclVendor::FinishDecl(clang::ObjCInterfaceDecl *interface_decl) {
   auto superclass_func = [interface_decl,
                           this](ObjCLanguageRuntime::ObjCISA isa) {
     clang::ObjCInterfaceDecl *superclass_decl = GetDeclForISA(isa);
 
     if (!superclass_decl)
       return;
 
     FinishDecl(superclass_decl);
-    clang::ASTContext &context = m_ast_ctx.getASTContext();
+    clang::ASTContext &context = m_ast_ctx->getASTContext();
     interface_decl->setSuperClass(context.getTrivialTypeSourceInfo(
         context.getObjCInterfaceType(superclass_decl)));
   };
 
   auto instance_method_func =
       [log, interface_decl, this](const char *name, const char *types) -> bool {
     if (!name || !types)
       return false; // skip this one
 
     ObjCRuntimeMethodType method_type(types);
 
     clang::ObjCMethodDecl *method_decl = method_type.BuildMethod(
-        m_ast_ctx, interface_decl, name, true, m_type_realizer_sp);
+        *m_ast_ctx, interface_decl, name, true, m_type_realizer_sp);
 
     LLDB_LOGF(log, "[  AOTV::FD] Instance method [%s] [%s]", name, types);
 
     if (method_decl)
       interface_decl->addDecl(method_decl);
 
     return false;
   };
 
   auto class_method_func = [log, interface_decl,
                             this](const char *name, const char *types) -> bool {
     if (!name || !types)
       return false; // skip this one
 
     ObjCRuntimeMethodType method_type(types);
 
     clang::ObjCMethodDecl *method_decl = method_type.BuildMethod(
-        m_ast_ctx, interface_decl, name, false, m_type_realizer_sp);
+        *m_ast_ctx, interface_decl, name, false, m_type_realizer_sp);
 
     LLDB_LOGF(log, "[  AOTV::FD] Class method [%s] [%s]", name, types);
 
     if (method_decl)
       interface_decl->addDecl(method_decl);
 
     return false;
   };
 
   auto ivar_func = [log, interface_decl,
                     this](const char *name, const char *type,
                           lldb::addr_t offset_ptr, uint64_t size) -> bool {
     if (!name || !type)
       return false;
 
     const bool for_expression = false;
 
     LLDB_LOGF(log,
               "[  AOTV::FD] Instance variable [%s] [%s], offset at %" PRIx64,
               name, type, offset_ptr);
 
     CompilerType ivar_type = m_runtime.GetEncodingToType()->RealizeType(
-        m_ast_ctx, type, for_expression);
+        *m_ast_ctx, type, for_expression);
 
     if (ivar_type.IsValid()) {
       clang::TypeSourceInfo *const type_source_info = nullptr;
       const bool is_synthesized = false;
       clang::ObjCIvarDecl *ivar_decl = clang::ObjCIvarDecl::Create(
-          m_ast_ctx.getASTContext(), interface_decl, clang::SourceLocation(),
-          clang::SourceLocation(), &m_ast_ctx.getASTContext().Idents.get(name),
+          m_ast_ctx->getASTContext(), interface_decl, clang::SourceLocation(),
+          clang::SourceLocation(), &m_ast_ctx->getASTContext().Idents.get(name),
           ClangUtil::GetQualType(ivar_type),
           type_source_info, // TypeSourceInfo *
           clang::ObjCIvarDecl::Public, nullptr, is_synthesized);
 
       if (ivar_decl) {
         interface_decl->addDecl(ivar_decl);
       }
     }
uint32_t AppleObjCDeclVendor::FindDecls(ConstString name, bool append,
   if (!append)
     decls.clear();
 
   uint32_t ret = 0;
 
   do {
     // See if the type is already in our ASTContext.
 
-    clang::ASTContext &ast_ctx = m_ast_ctx.getASTContext();
+    clang::ASTContext &ast_ctx = m_ast_ctx->getASTContext();
 
     clang::IdentifierInfo &identifier_info =
         ast_ctx.Idents.get(name.GetStringRef());
     clang::DeclarationName decl_name =
         ast_ctx.DeclarationNames.getIdentifier(&identifier_info);
 
     clang::DeclContext::lookup_result lookup_result =
         ast_ctx.getTranslationUnitDecl()->lookup(decl_name);
 
     if (!lookup_result.empty()) {
       if (clang::ObjCInterfaceDecl *result_iface_decl =
              llvm::dyn_cast<clang::ObjCInterfaceDecl>(*lookup_result.begin())) {
         if (log) {
           clang::QualType result_iface_type =
               ast_ctx.getObjCInterfaceType(result_iface_decl);
 
           uint64_t isa_value = LLDB_INVALID_ADDRESS;
-          ClangASTMetadata *metadata = m_ast_ctx.GetMetadata(result_iface_decl);
+          ClangASTMetadata *metadata = m_ast_ctx->GetMetadata(result_iface_decl);
           if (metadata)
             isa_value = metadata->GetISAPtr();
 
           LLDB_LOG(log,
                    "AOCTV::FT Found %s (isa 0x%" PRIx64 ") in the ASTContext",
                    result_iface_type.getAsString(), isa_value);
         }
 
-        decls.push_back(m_ast_ctx.GetCompilerDecl(result_iface_decl));
+        decls.push_back(m_ast_ctx->GetCompilerDecl(result_iface_decl));
         ret++;
         break;
       } else {
         LLDB_LOGF(log, "AOCTV::FT There's something in the ASTContext, but "
                        "it's not something we know about");
         break;
       }
     } else if (log) {
do {
 
     if (log) {
       clang::QualType new_iface_type = ast_ctx.getObjCInterfaceType(iface_decl);
 
       LLDB_LOG(log, "AOCTV::FT Created {1} (isa 0x{2:x})",
                new_iface_type.getAsString(), (uint64_t)isa);
     }
 
-    decls.push_back(m_ast_ctx.GetCompilerDecl(iface_decl));
+    decls.push_back(m_ast_ctx->GetCompilerDecl(iface_decl));
     ret++;
     break;
   } while (false);
 
   return ret;
 }

lldb/source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCTypeEncodingParser.cpp

 
 #include <vector>
 
 using namespace lldb_private;
 
 AppleObjCTypeEncodingParser::AppleObjCTypeEncodingParser(
     ObjCLanguageRuntime &runtime)
     : ObjCLanguageRuntime::EncodingToType(), m_runtime(runtime) {
-  if (!m_scratch_ast_ctx_up)
-    m_scratch_ast_ctx_up = std::make_unique<TypeSystemClang>(
-        "AppleObjCTypeEncodingParser ASTContext",
-        runtime.GetProcess()->GetTarget().GetArchitecture().GetTriple());
+  if (m_scratch_ast_ctx_sp)
+    return;
+
+  m_scratch_ast_ctx_sp = std::make_shared<TypeSystemClang>(
 }
 
 std::string AppleObjCTypeEncodingParser::ReadStructName(StringLexer &type) {
   StreamString buffer;
   while (type.HasAtLeast(1) && type.Peek() != '=')
     buffer.Printf("%c", type.Next());
   return std::string(buffer.GetString());
 }
clang::QualType AppleObjCTypeEncodingParser::BuildArray(
     TypeSystemClang &ast_ctx, StringLexer &type, bool for_expression) {
   if (!type.NextIf(_C_ARY_B))
     return clang::QualType();
   uint32_t size = ReadNumber(type);
   clang::QualType element_type(BuildType(ast_ctx, type, for_expression));
   if (!type.NextIf(_C_ARY_E))
     return clang::QualType();
   CompilerType array_type(ast_ctx.CreateArrayType(
-      CompilerType(&ast_ctx, element_type.getAsOpaquePtr()), size, false));
+      CompilerType(ast_ctx.weak_from_this(), element_type.getAsOpaquePtr()),
+      size, false));
   return ClangUtil::GetQualType(array_type);
 }
 
 // the runtime can emit these in the form of @"SomeType", giving more specifics
 // this would be interesting for expression parser interop, but since we
 // actually try to avoid exposing the ivar info to the expression evaluator,
 // consume but ignore the type info and always return an 'id'; if anything,
 // dynamic typing will resolve things for us anyway

lldb/source/Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.h

public:
   public:
     virtual ~EncodingToType();
 
     virtual CompilerType RealizeType(TypeSystemClang &ast_ctx, const char *name,
                                      bool for_expression) = 0;
     virtual CompilerType RealizeType(const char *name, bool for_expression);
 
   protected:
-    std::unique_ptr<TypeSystemClang> m_scratch_ast_ctx_up;
+    std::shared_ptr<TypeSystemClang> m_scratch_ast_ctx_sp;
   };
 
   class ObjCExceptionPrecondition : public BreakpointPrecondition {
   public:
     ObjCExceptionPrecondition();
 
     ~ObjCExceptionPrecondition() override = default;
 

lldb/source/Plugins/LanguageRuntime/ObjC/ObjCLanguageRuntime.cpp

if (isa) {
     }
   }
   return ClassDescriptorSP();
 }
 
 CompilerType
 ObjCLanguageRuntime::EncodingToType::RealizeType(const char *name,
                                                  bool for_expression) {
-  if (m_scratch_ast_ctx_up)
-    return RealizeType(*m_scratch_ast_ctx_up, name, for_expression);
+  if (m_scratch_ast_ctx_sp)
+    return RealizeType(*m_scratch_ast_ctx_sp, name, for_expression);
   return CompilerType();
 }
 
 ObjCLanguageRuntime::EncodingToType::~EncodingToType() = default;
 
 ObjCLanguageRuntime::EncodingToTypeSP ObjCLanguageRuntime::GetEncodingToType() {
   return nullptr;
 }

lldb/source/Plugins/Platform/FreeBSD/PlatformFreeBSD.h

MmapArgList GetMmapArgumentList(const ArchSpec &arch, lldb::addr_t addr,
                                   unsigned flags, lldb::addr_t fd,
                                   lldb::addr_t offset) override;
 
   CompilerType GetSiginfoType(const llvm::Triple &triple) override;
 
   std::vector<ArchSpec> m_supported_architectures;
 
 private:
-  std::unique_ptr<TypeSystemClang> m_type_system_up;
+  std::mutex m_mutex;
+  std::shared_ptr<TypeSystemClang> m_type_system;
 };
 
 } // namespace platform_freebsd
 } // namespace lldb_private
 
 #endif // LLDB_SOURCE_PLUGINS_PLATFORM_FREEBSD_PLATFORMFREEBSD_H

lldb/source/Plugins/Platform/FreeBSD/PlatformFreeBSD.cpp

MmapArgList PlatformFreeBSD::GetMmapArgumentList(const ArchSpec &arch,
 
   MmapArgList args({addr, length, prot, flags_platform, fd, offset});
   if (arch.GetTriple().getArch() == llvm::Triple::x86)
     args.push_back(0);
   return args;
 }
 
 CompilerType PlatformFreeBSD::GetSiginfoType(const llvm::Triple &triple) {
-  if (!m_type_system_up)
-    m_type_system_up.reset(new TypeSystemClang("siginfo", triple));
-  TypeSystemClang *ast = m_type_system_up.get();
+  {
+    std::lock_guard<std::mutex> guard(m_mutex);
+    if (!m_type_system)
+      m_type_system = std::make_shared<TypeSystemClang>("siginfo", triple);
+  }
+  TypeSystemClang *ast = m_type_system.get();
 
   // generic types
   CompilerType int_type = ast->GetBasicType(eBasicTypeInt);
   CompilerType uint_type = ast->GetBasicType(eBasicTypeUnsignedInt);
   CompilerType long_type = ast->GetBasicType(eBasicTypeLong);
   CompilerType voidp_type = ast->GetBasicType(eBasicTypeVoid).GetPointerType();
 
   // platform-specific types

lldb/source/Plugins/Platform/Linux/PlatformLinux.h

MmapArgList GetMmapArgumentList(const ArchSpec &arch, lldb::addr_t addr,
                                   unsigned flags, lldb::addr_t fd,
                                   lldb::addr_t offset) override;
 
   CompilerType GetSiginfoType(const llvm::Triple &triple) override;
 
   std::vector<ArchSpec> m_supported_architectures;
 
 private:
-  std::unique_ptr<TypeSystemClang> m_type_system_up;
+  std::mutex m_mutex;
+  std::shared_ptr<TypeSystemClang> m_type_system;
 };
 
 } // namespace platform_linux
 } // namespace lldb_private
 
 #endif // LLDB_SOURCE_PLUGINS_PLATFORM_LINUX_PLATFORMLINUX_H

lldb/source/Plugins/Platform/Linux/PlatformLinux.cpp

MmapArgList PlatformLinux::GetMmapArgumentList(const ArchSpec &arch,
   if (flags & eMmapFlagsAnon)
     flags_platform |= map_anon;
 
   MmapArgList args({addr, length, prot, flags_platform, fd, offset});
   return args;
 }
 
 CompilerType PlatformLinux::GetSiginfoType(const llvm::Triple &triple) {
-  if (!m_type_system_up)
-    m_type_system_up.reset(new TypeSystemClang("siginfo", triple));
-  TypeSystemClang *ast = m_type_system_up.get();
+  {
+    std::lock_guard<std::mutex> guard(m_mutex);
+    if (!m_type_system)
+      m_type_system = std::make_shared<TypeSystemClang>("siginfo", triple);
+  }
+  TypeSystemClang *ast = m_type_system.get();
 
   bool si_errno_then_code = true;
 
   switch (triple.getArch()) {
   case llvm::Triple::mips:
   case llvm::Triple::mipsel:
   case llvm::Triple::mips64:
   case llvm::Triple::mips64el:
     // mips has si_code and si_errno swapped

lldb/source/Plugins/Platform/NetBSD/PlatformNetBSD.h

MmapArgList GetMmapArgumentList(const ArchSpec &arch, lldb::addr_t addr,
                                   unsigned flags, lldb::addr_t fd,
                                   lldb::addr_t offset) override;
 
   CompilerType GetSiginfoType(const llvm::Triple &triple) override;
 
   std::vector<ArchSpec> m_supported_architectures;
 
 private:
-  std::unique_ptr<TypeSystemClang> m_type_system_up;
+  std::mutex m_mutex;
+  std::shared_ptr<TypeSystemClang> m_type_system;
 };
 
 } // namespace platform_netbsd
 } // namespace lldb_private
 
 #endif // LLDB_SOURCE_PLUGINS_PLATFORM_NETBSD_PLATFORMNETBSD_H

lldb/source/Plugins/Platform/NetBSD/PlatformNetBSD.cpp

MmapArgList PlatformNetBSD::GetMmapArgumentList(const ArchSpec &arch,
   if (flags & eMmapFlagsAnon)
     flags_platform |= MAP_ANON;
 
   MmapArgList args({addr, length, prot, flags_platform, fd, offset});
   return args;
 }
 
 CompilerType PlatformNetBSD::GetSiginfoType(const llvm::Triple &triple) {
-  if (!m_type_system_up)
-    m_type_system_up.reset(new TypeSystemClang("siginfo", triple));
-  TypeSystemClang *ast = m_type_system_up.get();
+  {
+    std::lock_guard<std::mutex> guard(m_mutex);
+    if (!m_type_system)
+      m_type_system = std::make_shared<TypeSystemClang>("siginfo", triple);
+  }
+  TypeSystemClang *ast = m_type_system.get();
 
   // generic types
   CompilerType int_type = ast->GetBasicType(eBasicTypeInt);
   CompilerType uint_type = ast->GetBasicType(eBasicTypeUnsignedInt);
   CompilerType long_type = ast->GetBasicType(eBasicTypeLong);
   CompilerType long_long_type = ast->GetBasicType(eBasicTypeLongLong);
   CompilerType voidp_type = ast->GetBasicType(eBasicTypeVoid).GetPointerType();
 

lldb/source/Plugins/Process/Utility/InferiorCallPOSIX.cpp

if (sc_list.GetContextAtIndex(0, sc)) {
                              mmap_range)) {
         auto type_system_or_err =
             process->GetTarget().GetScratchTypeSystemForLanguage(
                 eLanguageTypeC);
         if (!type_system_or_err) {
           llvm::consumeError(type_system_or_err.takeError());
           return false;
         }
+        auto ts = *type_system_or_err;
+        if (!ts)
+          return false;
         CompilerType void_ptr_type =
-            type_system_or_err->GetBasicTypeFromAST(eBasicTypeVoid)
-                .GetPointerType();
+            ts->GetBasicTypeFromAST(eBasicTypeVoid).GetPointerType();
         const ArchSpec arch = process->GetTarget().GetArchitecture();
         MmapArgList args =
             process->GetTarget().GetPlatform()->GetMmapArgumentList(
                 arch, addr, length, prot_arg, flags, fd, offset);
         lldb::ThreadPlanSP call_plan_sp(
             new ThreadPlanCallFunction(*thread, mmap_range.GetBaseAddress(),
                                        void_ptr_type, args, options));
         if (call_plan_sp) {

lldb/source/Plugins/SymbolFile/Breakpad/SymbolFileBreakpad.h

void FindTypes(ConstString name, const CompilerDeclContext &parent_decl_ctx,
                  uint32_t max_matches,
                  llvm::DenseSet<SymbolFile *> &searched_symbol_files,
                  TypeMap &types) override;
 
   void FindTypes(llvm::ArrayRef<CompilerContext> pattern, LanguageSet languages,
                  llvm::DenseSet<SymbolFile *> &searched_symbol_files,
                  TypeMap &types) override;
 
-  llvm::Expected<TypeSystem &>
+  llvm::Expected<lldb::TypeSystemSP>
   GetTypeSystemForLanguage(lldb::LanguageType language) override {
     return llvm::make_error<llvm::StringError>(
         "SymbolFileBreakpad does not support GetTypeSystemForLanguage",
         llvm::inconvertibleErrorCode());
   }
 
   CompilerDeclContext
   FindNamespace(ConstString name,

lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp

TypeSP DWARFASTParserClang::ParseTypeFromClangModule(const SymbolContext &sc,
   return type_sp;
 }
 
 static void ForcefullyCompleteType(CompilerType type) {
   bool started = TypeSystemClang::StartTagDeclarationDefinition(type);
   lldbassert(started && "Unable to start a class type definition.");
   TypeSystemClang::CompleteTagDeclarationDefinition(type);
   const clang::TagDecl *td = ClangUtil::GetAsTagDecl(type);
-  auto &ts = llvm::cast<TypeSystemClang>(*type.GetTypeSystem());
-  ts.GetMetadata(td)->SetIsForcefullyCompleted();
+  auto ts_sp = type.GetTypeSystem();
+  auto ts = ts_sp.dyn_cast_or_null<TypeSystemClang>();
+  if (ts)
+    ts->GetMetadata(td)->SetIsForcefullyCompleted();
 }
 
 /// This function serves a similar purpose as RequireCompleteType above, but it
 /// avoids completing the type if it is not immediately necessary. It only
 /// ensures we _can_ complete the type later.
 static void PrepareContextToReceiveMembers(TypeSystemClang &ast,
                                            ClangASTImporter &ast_importer,
                                            clang::DeclContext *decl_ctx,
if (type_sp) {
       return type_sp;
     }
   }
   DEBUG_PRINTF("0x%8.8" PRIx64 ": %s (\"%s\")\n", die.GetID(),
                DW_TAG_value_to_name(tag), type_name_cstr);
 
   CompilerType enumerator_clang_type;
   CompilerType clang_type;
-  clang_type.SetCompilerType(
-      &m_ast, dwarf->GetForwardDeclDieToClangType().lookup(die.GetDIE()));
+  clang_type =
+      CompilerType(m_ast.weak_from_this(),
+                   dwarf->GetForwardDeclDieToClangType().lookup(die.GetDIE()));
   if (!clang_type) {
     if (attrs.type.IsValid()) {
       Type *enumerator_type =
           dwarf->ResolveTypeUID(attrs.type.Reference(), true);
       if (enumerator_type)
         enumerator_clang_type = enumerator_type->GetFullCompilerType();
     }
 

 }
 
 void DWARFASTParserClang::ParseInheritance(
     const DWARFDIE &die, const DWARFDIE &parent_die,
     const CompilerType class_clang_type, const AccessType default_accessibility,
     const lldb::ModuleSP &module_sp,
     std::vector<std::unique_ptr<clang::CXXBaseSpecifier>> &base_classes,
     ClangASTImporter::LayoutInfo &layout_info) {
-
-  TypeSystemClang *ast =
-      llvm::dyn_cast_or_null<TypeSystemClang>(class_clang_type.GetTypeSystem());
+  auto ast =
+      class_clang_type.GetTypeSystem().dyn_cast_or_null<TypeSystemClang>();
   if (ast == nullptr)
     return;
 
   // TODO: implement DW_TAG_inheritance type parsing.
   DWARFAttributes attributes;
   const size_t num_attributes = die.GetAttributes(attributes);
   if (num_attributes == 0)
     return;
if (type_sp) {
       if (defn_decl_ctx)
         LinkDeclContextToDIE(defn_decl_ctx, die);
       return type_sp;
     }
   }
   assert(tag_decl_kind != -1);
   (void)tag_decl_kind;
   bool clang_type_was_created = false;
-  clang_type.SetCompilerType(
-      &m_ast, dwarf->GetForwardDeclDieToClangType().lookup(die.GetDIE()));
+  clang_type =
+      CompilerType(m_ast.weak_from_this(),
+                   dwarf->GetForwardDeclDieToClangType().lookup(die.GetDIE()));
   if (!clang_type) {
     clang::DeclContext *decl_ctx =
         GetClangDeclContextContainingDIE(die, nullptr);
 
     PrepareContextToReceiveMembers(m_ast, GetClangASTImporter(), decl_ctx, die,
                                    attrs.name.GetCString());
 
     if (attrs.accessibility == eAccessNone && decl_ctx) {
delayed_properties.push_back(DelayedAddObjCClassProperty(
       member_type->GetLayoutCompilerType(), propAttrs.prop_setter_name,
       propAttrs.prop_getter_name, propAttrs.prop_attributes, &metadata));
 }
 
 llvm::Expected<llvm::APInt> DWARFASTParserClang::ExtractIntFromFormValue(
     const CompilerType &int_type, const DWARFFormValue &form_value) const {
   clang::QualType qt = ClangUtil::GetQualType(int_type);
   assert(qt->isIntegralOrEnumerationType());
-  TypeSystemClang &ts = *llvm::cast<TypeSystemClang>(int_type.GetTypeSystem());
+  auto ts_ptr = int_type.GetTypeSystem().dyn_cast_or_null<TypeSystemClang>();
+  if (!ts_ptr)
+    return llvm::createStringError(llvm::inconvertibleErrorCode(),
+                                   "TypeSystem not clang");
+  TypeSystemClang &ts = *ts_ptr;
   clang::ASTContext &ast = ts.getASTContext();
 
   const unsigned type_bits = ast.getIntWidth(qt);
   const bool is_unsigned = qt->isUnsignedIntegerType();
 
   // The maximum int size supported at the moment by this function. Limited
   // by the uint64_t return type of DWARFFormValue::Signed/Unsigned.
   constexpr std::size_t max_bit_size = 64;
bool DWARFASTParserClang::ParseChildMembers(
     const AccessType default_accessibility,
     ClangASTImporter::LayoutInfo &layout_info) {
   if (!parent_die)
     return false;
 
   FieldInfo last_field_info;
 
   ModuleSP module_sp = parent_die.GetDWARF()->GetObjectFile()->GetModule();
-  TypeSystemClang *ast =
-      llvm::dyn_cast_or_null<TypeSystemClang>(class_clang_type.GetTypeSystem());
+  auto ts = class_clang_type.GetTypeSystem();
+  auto ast = ts.dyn_cast_or_null<TypeSystemClang>();
   if (ast == nullptr)
     return false;
 
   for (DWARFDIE die : parent_die.children()) {
     dw_tag_t tag = die.Tag();
 
     switch (tag) {
     case DW_TAG_APPLE_property:

lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h

void FindTypes(llvm::ArrayRef<lldb_private::CompilerContext> pattern,
                  lldb_private::LanguageSet languages,
                  llvm::DenseSet<SymbolFile *> &searched_symbol_files,
                  lldb_private::TypeMap &types) override;
 
   void GetTypes(lldb_private::SymbolContextScope *sc_scope,
                 lldb::TypeClass type_mask,
                 lldb_private::TypeList &type_list) override;
 
-  llvm::Expected<lldb_private::TypeSystem &>
+  llvm::Expected<lldb::TypeSystemSP>
   GetTypeSystemForLanguage(lldb::LanguageType language) override;
 
   lldb_private::CompilerDeclContext FindNamespace(
       lldb_private::ConstString name,
       const lldb_private::CompilerDeclContext &parent_decl_ctx) override;
 
   void PreloadSymbols() override;
 
public:
   void DumpClangAST(lldb_private::Stream &s) override;
 
   lldb_private::DWARFContext &GetDWARFContext() { return m_context; }
 
   const std::shared_ptr<SymbolFileDWARFDwo> &GetDwpSymbolFile();
 
   lldb_private::FileSpec GetFile(DWARFUnit &unit, size_t file_idx);
 
-  static llvm::Expected<lldb_private::TypeSystem &>
-  GetTypeSystem(DWARFUnit &unit);
+  static llvm::Expected<lldb::TypeSystemSP> GetTypeSystem(DWARFUnit &unit);
 
   static DWARFASTParser *GetDWARFParser(DWARFUnit &unit);
 
   // CompilerDecl related functions
 
   static lldb_private::CompilerDecl GetDecl(const DWARFDIE &die);
 
   static lldb_private::CompilerDeclContext GetDeclContext(const DWARFDIE &die);

lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp

 UniqueDWARFASTTypeMap &SymbolFileDWARF::GetUniqueDWARFASTTypeMap() {
   SymbolFileDWARFDebugMap *debug_map_symfile = GetDebugMapSymfile();
   if (debug_map_symfile)
     return debug_map_symfile->GetUniqueDWARFASTTypeMap();
   else
     return m_unique_ast_type_map;
 }
 
-llvm::Expected<TypeSystem &>
+llvm::Expected<lldb::TypeSystemSP>
 SymbolFileDWARF::GetTypeSystemForLanguage(LanguageType language) {
   if (SymbolFileDWARFDebugMap *debug_map_symfile = GetDebugMapSymfile())
     return debug_map_symfile->GetTypeSystemForLanguage(language);
 
   auto type_system_or_err =
       m_objfile_sp->GetModule()->GetTypeSystemForLanguage(language);
-  if (type_system_or_err) {
-    type_system_or_err->SetSymbolFile(this);
-  }
+  if (type_system_or_err)
+    if (auto ts = *type_system_or_err)
+      ts->SetSymbolFile(this);
   return type_system_or_err;
 }
 
 void SymbolFileDWARF::InitializeObject() {
   Log *log = GetLog(DWARFLog::DebugInfo);
 
   InitializeFirstCodeAddress();
 
if (!die.IsValid())
     return nullptr;
 
   auto type_system_or_err = GetTypeSystemForLanguage(GetLanguage(*die.GetCU()));
   if (auto err = type_system_or_err.takeError()) {
     LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
                    "Unable to parse function");
     return nullptr;
   }
-  DWARFASTParser *dwarf_ast = type_system_or_err->GetDWARFParser();
+  auto ts = *type_system_or_err;
+  if (!ts)
+    return nullptr;
+  DWARFASTParser *dwarf_ast = ts->GetDWARFParser();
   if (!dwarf_ast)
     return nullptr;
 
   DWARFRangeList ranges;
   if (die.GetDIE()->GetAttributeAddressRanges(die.GetCU(), ranges,
                                               /*check_hi_lo_pc=*/true) == 0)
     return nullptr;
 
SymbolFileDWARF::ConstructFunctionDemangledName(const DWARFDIE &die) {
 
   auto type_system_or_err = GetTypeSystemForLanguage(GetLanguage(*die.GetCU()));
   if (auto err = type_system_or_err.takeError()) {
     LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
                    "Unable to construct demangled name for function");
     return ConstString();
   }
 
-  DWARFASTParser *dwarf_ast = type_system_or_err->GetDWARFParser();
+  auto ts = *type_system_or_err;
+  if (!ts) {
+    LLDB_LOG(GetLog(LLDBLog::Symbols), "Type system no longer live");
+    return ConstString();
+  }
+  DWARFASTParser *dwarf_ast = ts->GetDWARFParser();
   if (!dwarf_ast)
     return ConstString();
 
   return dwarf_ast->ConstructDemangledNameFromDWARF(die);
 }
 
 lldb::addr_t SymbolFileDWARF::FixupAddress(lldb::addr_t file_addr) {
   SymbolFileDWARFDebugMap *debug_map_symfile = GetDebugMapSymfile();

 bool SymbolFileDWARF::HasForwardDeclForClangType(
     const CompilerType &compiler_type) {
   CompilerType compiler_type_no_qualifiers =
       ClangUtil::RemoveFastQualifiers(compiler_type);
   if (GetForwardDeclClangTypeToDie().count(
           compiler_type_no_qualifiers.GetOpaqueQualType())) {
     return true;
   }
-  TypeSystem *type_system = compiler_type.GetTypeSystem();
-
-  TypeSystemClang *clang_type_system =
-      llvm::dyn_cast_or_null<TypeSystemClang>(type_system);
+  auto type_system = compiler_type.GetTypeSystem();
+  auto clang_type_system = type_system.dyn_cast_or_null<TypeSystemClang>();
   if (!clang_type_system)
     return false;
   DWARFASTParserClang *ast_parser =
       static_cast<DWARFASTParserClang *>(clang_type_system->GetDWARFParser());
   return ast_parser->GetClangASTImporter().CanImport(compiler_type);
 }
 
 bool SymbolFileDWARF::CompleteType(CompilerType &compiler_type) {
   std::lock_guard<std::recursive_mutex> guard(GetModuleMutex());
-
-  TypeSystemClang *clang_type_system =
-      llvm::dyn_cast_or_null<TypeSystemClang>(compiler_type.GetTypeSystem());
+  auto clang_type_system =
+      compiler_type.GetTypeSystem().dyn_cast_or_null<TypeSystemClang>();
   if (clang_type_system) {
     DWARFASTParserClang *ast_parser =
         static_cast<DWARFASTParserClang *>(clang_type_system->GetDWARFParser());
     if (ast_parser &&
         ast_parser->GetClangASTImporter().CanImport(compiler_type))
       return ast_parser->GetClangASTImporter().CompleteType(compiler_type);
   }
 
bool SymbolFileDWARF::DeclContextMatchesThisSymbolFile(
   auto type_system_or_err = GetTypeSystemForLanguage(
       decl_ctx_type_system->GetMinimumLanguage(nullptr));
   if (auto err = type_system_or_err.takeError()) {
     LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
                    "Unable to match namespace decl using TypeSystem");
     return false;
   }
 
-  if (decl_ctx_type_system == &type_system_or_err.get())
+  if (decl_ctx_type_system == type_system_or_err->get())
     return true; // The type systems match, return true
 
   // The namespace AST was valid, and it does not match...
   Log *log = GetLog(DWARFLog::Lookups);
 
   if (log)
     GetObjectFile()->GetModule()->LogMessage(
         log, "Valid namespace does not match symbol file");
if (type_name) {
             DW_TAG_value_to_name(dwarf_decl_ctx[0].tag),
             dwarf_decl_ctx.GetQualifiedName());
       }
 
       // Get the type system that we are looking to find a type for. We will
       // use this to ensure any matches we find are in a language that this
       // type system supports
       const LanguageType language = dwarf_decl_ctx.GetLanguage();
-      TypeSystem *type_system = nullptr;
+      TypeSystemSP type_system = nullptr;
       if (language != eLanguageTypeUnknown) {
         auto type_system_or_err = GetTypeSystemForLanguage(language);
         if (auto err = type_system_or_err.takeError()) {
           LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
                          "Cannot get TypeSystem for language {}",
                          Language::GetNameForLanguageType(language));
         } else {
-          type_system = &type_system_or_err.get();
+          type_system = *type_system_or_err;
         }
       }
 
       m_index->GetTypes(dwarf_decl_ctx, [&](DWARFDIE type_die) {
         // Make sure type_die's language matches the type system we are
         // looking for. We don't want to find a "Foo" type from Java if we
         // are looking for a "Foo" type for C, C++, ObjC, or ObjC++.
         if (type_system &&
if (!die)
     return {};
 
   auto type_system_or_err = GetTypeSystemForLanguage(GetLanguage(*die.GetCU()));
   if (auto err = type_system_or_err.takeError()) {
     LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
                    "Unable to parse type");
     return {};
   }
+  auto ts = *type_system_or_err;
+  if (!ts)
+    return {};
 
-  DWARFASTParser *dwarf_ast = type_system_or_err->GetDWARFParser();
+  DWARFASTParser *dwarf_ast = ts->GetDWARFParser();
   if (!dwarf_ast)
     return {};
 
   TypeSP type_sp = dwarf_ast->ParseTypeFromDWARF(sc, die, type_is_new_ptr);
   if (type_sp) {
     GetTypeList().Insert(type_sp);
 
     if (die.Tag() == DW_TAG_subprogram) {
void SymbolFileDWARF::Dump(lldb_private::Stream &s) {
   SymbolFileCommon::Dump(s);
   m_index->Dump(s);
 }
 
 void SymbolFileDWARF::DumpClangAST(Stream &s) {
   auto ts_or_err = GetTypeSystemForLanguage(eLanguageTypeC_plus_plus);
   if (!ts_or_err)
     return;
-  TypeSystemClang *clang =
-      llvm::dyn_cast_or_null<TypeSystemClang>(&ts_or_err.get());
+  auto ts = *ts_or_err;
+  TypeSystemClang *clang = llvm::dyn_cast_or_null<TypeSystemClang>(ts.get());
   if (!clang)
     return;
   clang->Dump(s.AsRawOstream());
 }
 
 SymbolFileDWARFDebugMap *SymbolFileDWARF::GetDebugMapSymfile() {
   if (m_debug_map_symfile == nullptr) {
     lldb::ModuleSP module_sp(m_debug_map_module_wp.lock());
if (FileSystem::Instance().Exists(dwp_filespec)) {
         return;
       m_dwp_symfile =
           std::make_shared<SymbolFileDWARFDwo>(*this, dwp_obj_file, 0x3fffffff);
     }
   });
   return m_dwp_symfile;
 }
 
-llvm::Expected<TypeSystem &> SymbolFileDWARF::GetTypeSystem(DWARFUnit &unit) {
+llvm::Expected<lldb::TypeSystemSP>
+SymbolFileDWARF::GetTypeSystem(DWARFUnit &unit) {
   return unit.GetSymbolFileDWARF().GetTypeSystemForLanguage(GetLanguage(unit));
 }
 
 DWARFASTParser *SymbolFileDWARF::GetDWARFParser(DWARFUnit &unit) {
   auto type_system_or_err = GetTypeSystem(unit);
   if (auto err = type_system_or_err.takeError()) {
     LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
                    "Unable to get DWARFASTParser");
     return nullptr;
   }
-  return type_system_or_err->GetDWARFParser();
+  if (auto ts = *type_system_or_err)
+    return ts->GetDWARFParser();
+  return nullptr;
 }
 
 CompilerDecl SymbolFileDWARF::GetDecl(const DWARFDIE &die) {
   if (DWARFASTParser *dwarf_ast = GetDWARFParser(*die.GetCU()))
     return dwarf_ast->GetDeclForUIDFromDWARF(die);
   return CompilerDecl();
 }
 

lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.h

public:
 
   ~SymbolFileDWARFDwo() override = default;
 
   DWARFCompileUnit *GetDWOCompileUnitForHash(uint64_t hash);
 
   void GetObjCMethods(lldb_private::ConstString class_name,
                       llvm::function_ref<bool(DWARFDIE die)> callback) override;
 
-  llvm::Expected<lldb_private::TypeSystem &>
+  llvm::Expected<lldb::TypeSystemSP>
   GetTypeSystemForLanguage(lldb::LanguageType language) override;
 
   DWARFDIE
   GetDIE(const DIERef &die_ref) override;
 
   llvm::Optional<uint32_t> GetDwoNum() override { return GetID() >> 32; }
 
 protected:

lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.cpp

 
 lldb::TypeSP SymbolFileDWARFDwo::FindCompleteObjCDefinitionTypeForDIE(
     const DWARFDIE &die, lldb_private::ConstString type_name,
     bool must_be_implementation) {
   return GetBaseSymbolFile().FindCompleteObjCDefinitionTypeForDIE(
       die, type_name, must_be_implementation);
 }
 
-llvm::Expected<TypeSystem &>
+llvm::Expected<lldb::TypeSystemSP>
 SymbolFileDWARFDwo::GetTypeSystemForLanguage(LanguageType language) {
   return GetBaseSymbolFile().GetTypeSystemForLanguage(language);
 }
 
 DWARFDIE
 SymbolFileDWARFDwo::GetDIE(const DIERef &die_ref) {
   if (die_ref.dwo_num() == GetDwoNum())
     return DebugInfo().GetDIE(die_ref);
   return GetBaseSymbolFile().GetDIE(die_ref);
 }

lldb/source/Plugins/SymbolFile/NativePDB/PdbAstBuilder.cpp

void PdbAstBuilder::ParseDeclsForContext(clang::DeclContext &context) {
   }
 }
 
 CompilerDecl PdbAstBuilder::ToCompilerDecl(clang::Decl &decl) {
   return m_clang.GetCompilerDecl(&decl);
 }
 
 CompilerType PdbAstBuilder::ToCompilerType(clang::QualType qt) {
-  return {&m_clang, qt.getAsOpaquePtr()};
+  return {m_clang.weak_from_this(), qt.getAsOpaquePtr()};
 }
 
 CompilerDeclContext
 PdbAstBuilder::ToCompilerDeclContext(clang::DeclContext &context) {
   return m_clang.CreateDeclContext(&context);
 }
 
 clang::Decl * PdbAstBuilder::FromCompilerDecl(CompilerDecl decl) {

lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.h

void FindTypes(ConstString name, const CompilerDeclContext &parent_decl_ctx,
                  uint32_t max_matches,
                  llvm::DenseSet<SymbolFile *> &searched_symbol_files,
                  TypeMap &types) override;
 
   void FindTypes(llvm::ArrayRef<CompilerContext> pattern, LanguageSet languages,
                  llvm::DenseSet<SymbolFile *> &searched_symbol_files,
                  TypeMap &types) override;
 
-  llvm::Expected<TypeSystem &>
+  llvm::Expected<lldb::TypeSystemSP>
   GetTypeSystemForLanguage(lldb::LanguageType language) override;
 
   CompilerDeclContext
   FindNamespace(ConstString name,
                 const CompilerDeclContext &parent_decl_ctx) override;
 
   llvm::StringRef GetPluginName() override { return GetPluginNameStatic(); }
 

lldb/source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp

void SymbolFileNativePDB::InitializeObject() {
   m_index->ParseSectionContribs();
 
   auto ts_or_err = m_objfile_sp->GetModule()->GetTypeSystemForLanguage(
       lldb::eLanguageTypeC_plus_plus);
   if (auto err = ts_or_err.takeError()) {
     LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
                    "Failed to initialize");
   } else {
-    ts_or_err->SetSymbolFile(this);
+    if (auto ts = *ts_or_err)
+      ts->SetSymbolFile(this);
     BuildParentMap();
   }
 }
 
 uint32_t SymbolFileNativePDB::CalculateNumCompileUnits() {
   const DbiModuleList &modules = m_index->dbi().modules();
   uint32_t count = modules.getModuleCount();
   if (count == 0)
Block &SymbolFileNativePDB::CreateBlock(PdbCompilandSymId block_id) {
   CompilandIndexItem *cii = m_index->compilands().GetCompiland(block_id.modi);
   CVSymbol sym = cii->m_debug_stream.readSymbolAtOffset(block_id.offset);
   CompUnitSP comp_unit = GetOrCreateCompileUnit(*cii);
   lldb::user_id_t opaque_block_uid = toOpaqueUid(block_id);
   BlockSP child_block = std::make_shared<Block>(opaque_block_uid);
   auto ts_or_err = GetTypeSystemForLanguage(comp_unit->GetLanguage());
   if (auto err = ts_or_err.takeError())
     return *child_block;
-  PdbAstBuilder* ast_builder = ts_or_err->GetNativePDBParser();
+  auto ts = *ts_or_err;
+  if (!ts)
+    return *child_block;
+  PdbAstBuilder* ast_builder = ts->GetNativePDBParser();
 
   switch (sym.kind()) {
   case S_GPROC32:
   case S_LPROC32: {
     // This is a function.  It must be global.  Creating the Function entry
     // for it automatically creates a block for it.
     FunctionSP func = GetOrCreateFunction(block_id, *comp_unit);
     if (func) {
FunctionSP func_sp = std::make_shared<Function>(
       &comp_unit, toOpaqueUid(func_id), toOpaqueUid(sig_id), mangled,
       func_type.get(), func_range);
 
   comp_unit.AddFunction(func_sp);
 
   auto ts_or_err = GetTypeSystemForLanguage(comp_unit.GetLanguage());
   if (auto err = ts_or_err.takeError())
     return func_sp;
-  ts_or_err->GetNativePDBParser()->GetOrCreateFunctionDecl(func_id);
+  auto ts = *ts_or_err;
+  if (!ts)
+    return func_sp;
+  ts->GetNativePDBParser()->GetOrCreateFunctionDecl(func_id);
 
   return func_sp;
 }
 
 CompUnitSP
 SymbolFileNativePDB::CreateCompileUnit(const CompilandIndexItem &cci) {
   lldb::LanguageType lang =
       cci.m_compile_opts ? TranslateLanguage(cci.m_compile_opts->getLanguage())
else if (*expected_full_ti != type_id.index) {
       }
     }
   }
 
   PdbTypeSymId best_decl_id = full_decl_uid ? *full_decl_uid : type_id;
   auto ts_or_err = GetTypeSystemForLanguage(lldb::eLanguageTypeC_plus_plus);
   if (auto err = ts_or_err.takeError())
     return nullptr;
-  PdbAstBuilder* ast_builder = ts_or_err->GetNativePDBParser();
+  auto ts = *ts_or_err;
+  if (!ts)
+    return nullptr;
+
+  PdbAstBuilder* ast_builder = ts->GetNativePDBParser();
   clang::QualType qt = ast_builder->GetOrCreateType(best_decl_id);
   if (qt.isNull())
     return nullptr;
 
   TypeSP result = CreateType(best_decl_id, ast_builder->ToCompilerType(qt));
   if (!result)
     return nullptr;
 
VariableSP SymbolFileNativePDB::CreateGlobalVariable(PdbGlobalSymId var_id) {
   Declaration decl;
   PdbTypeSymId tid(ti, false);
   SymbolFileTypeSP type_sp =
       std::make_shared<SymbolFileType>(*this, toOpaqueUid(tid));
   Variable::RangeList ranges;
   auto ts_or_err = GetTypeSystemForLanguage(comp_unit->GetLanguage());
   if (auto err = ts_or_err.takeError())
     return nullptr;
-  ts_or_err->GetNativePDBParser()->GetOrCreateVariableDecl(var_id);
+  auto ts = *ts_or_err;
+  if (!ts)
+    return nullptr;
+
+  ts->GetNativePDBParser()->GetOrCreateVariableDecl(var_id);
 
   ModuleSP module_sp = GetObjectFile()->GetModule();
   DWARFExpressionList location(
       module_sp, MakeGlobalLocationExpression(section, offset, module_sp),
       nullptr);
 
   std::string global_name("::");
   global_name += name;
size_t SymbolFileNativePDB::ParseSymbolArrayInScope(
 
   return count;
 }
 
 void SymbolFileNativePDB::DumpClangAST(Stream &s) {
   auto ts_or_err = GetTypeSystemForLanguage(eLanguageTypeC_plus_plus);
   if (!ts_or_err)
     return;
-  TypeSystemClang *clang =
-      llvm::dyn_cast_or_null<TypeSystemClang>(&ts_or_err.get());
+  auto ts = *ts_or_err;
+  TypeSystemClang *clang = llvm::dyn_cast_or_null<TypeSystemClang>(ts.get());
   if (!clang)
     return;
   clang->GetNativePDBParser()->Dump(s);
 }
 
 void SymbolFileNativePDB::FindGlobalVariables(
     ConstString name, const CompilerDeclContext &parent_decl_ctx,
     uint32_t max_matches, VariableList &variables) {
VariableSP SymbolFileNativePDB::CreateLocalVariable(PdbCompilandSymId scope_id,
   VariableSP var_sp = std::make_shared<Variable>(
       toOpaqueUid(var_id), name.c_str(), name.c_str(), sftype, var_scope,
       &block, scope_ranges, &decl, var_info.location, external, artificial,
       location_is_constant_data, static_member);
   if (!is_param) {
     auto ts_or_err = GetTypeSystemForLanguage(comp_unit_sp->GetLanguage());
     if (auto err = ts_or_err.takeError())
       return nullptr;
-    ts_or_err->GetNativePDBParser()->GetOrCreateVariableDecl(scope_id, var_id);
+    auto ts = *ts_or_err;
+    if (!ts)
+      return nullptr;
+
+    ts->GetNativePDBParser()->GetOrCreateVariableDecl(scope_id, var_id);
   }
   m_local_variables[toOpaqueUid(var_id)] = var_sp;
   return var_sp;
 }
 
 VariableSP SymbolFileNativePDB::GetOrCreateLocalVariable(
     PdbCompilandSymId scope_id, PdbCompilandSymId var_id, bool is_param) {
   auto iter = m_local_variables.find(toOpaqueUid(var_id));
TypeSP SymbolFileNativePDB::CreateTypedef(PdbGlobalSymId id) {
 
   UDTSym udt = llvm::cantFail(SymbolDeserializer::deserializeAs<UDTSym>(sym));
 
   TypeSP target_type = GetOrCreateType(udt.Type);
 
   auto ts_or_err = GetTypeSystemForLanguage(lldb::eLanguageTypeC_plus_plus);
   if (auto err = ts_or_err.takeError())
     return nullptr;
-  ts_or_err->GetNativePDBParser()->GetOrCreateTypedefDecl(id);
+  auto ts = *ts_or_err;
+  if (!ts)
+    return nullptr;
+
+  ts->GetNativePDBParser()->GetOrCreateTypedefDecl(id);
 
   Declaration decl;
   return std::make_shared<lldb_private::Type>(
       toOpaqueUid(id), this, ConstString(udt.Name),
       target_type->GetByteSize(nullptr), nullptr, target_type->GetID(),
       lldb_private::Type::eEncodingIsTypedefUID, decl,
       target_type->GetForwardCompilerType(),
       lldb_private::Type::ResolveState::Forward);
size_t SymbolFileNativePDB::ParseVariablesForContext(const SymbolContext &sc) {
 
   llvm_unreachable("Unreachable!");
 }
 
 CompilerDecl SymbolFileNativePDB::GetDeclForUID(lldb::user_id_t uid) {
   auto ts_or_err = GetTypeSystemForLanguage(lldb::eLanguageTypeC_plus_plus);
   if (auto err = ts_or_err.takeError())
     return CompilerDecl();
-  if (auto decl = ts_or_err->GetNativePDBParser()->GetOrCreateDeclForUid(uid))
+  auto ts = *ts_or_err;
+  if (!ts)
+    return {};
+
+  if (auto decl = ts->GetNativePDBParser()->GetOrCreateDeclForUid(uid))
     return *decl;
   return CompilerDecl();
 }
 
 CompilerDeclContext
 SymbolFileNativePDB::GetDeclContextForUID(lldb::user_id_t uid) {
   auto ts_or_err = GetTypeSystemForLanguage(lldb::eLanguageTypeC_plus_plus);
   if (auto err = ts_or_err.takeError())
     return {};
-  PdbAstBuilder *ast_builder = ts_or_err->GetNativePDBParser();
+  auto ts = *ts_or_err;
+  if (!ts)
+    return {};
+
+  PdbAstBuilder *ast_builder = ts->GetNativePDBParser();
   clang::DeclContext *context =
       ast_builder->GetOrCreateDeclContextForUid(PdbSymUid(uid));
   if (!context)
     return {};
 
   return ast_builder->ToCompilerDeclContext(*context);
 }
 
 CompilerDeclContext
 SymbolFileNativePDB::GetDeclContextContainingUID(lldb::user_id_t uid) {
   auto ts_or_err = GetTypeSystemForLanguage(lldb::eLanguageTypeC_plus_plus);
   if (auto err = ts_or_err.takeError())
     return CompilerDeclContext();
-  PdbAstBuilder *ast_builder = ts_or_err->GetNativePDBParser();
+  auto ts = *ts_or_err;
+  if (!ts)
+    return {};
+
+  PdbAstBuilder *ast_builder = ts->GetNativePDBParser();
   clang::DeclContext *context = ast_builder->GetParentDeclContext(PdbSymUid(uid));
   if (!context)
     return CompilerDeclContext();
   return ast_builder->ToCompilerDeclContext(*context);
 }
 
 Type *SymbolFileNativePDB::ResolveTypeUID(lldb::user_id_t type_uid) {
   std::lock_guard<std::recursive_mutex> guard(GetModuleMutex());

 llvm::Optional<SymbolFile::ArrayInfo>
 SymbolFileNativePDB::GetDynamicArrayInfoForUID(
     lldb::user_id_t type_uid, const lldb_private::ExecutionContext *exe_ctx) {
   return llvm::None;
 }
 
 bool SymbolFileNativePDB::CompleteType(CompilerType &compiler_type) {
   std::lock_guard<std::recursive_mutex> guard(GetModuleMutex());
-
-  TypeSystemClang *clang_type_system =
-      llvm::dyn_cast_or_null<TypeSystemClang>(compiler_type.GetTypeSystem());
+  auto ts = compiler_type.GetTypeSystem();
+  auto clang_type_system = ts.dyn_cast_or_null<TypeSystemClang>();
   if (!clang_type_system)
     return false;
 
   PdbAstBuilder *ast_builder =
       static_cast<PdbAstBuilder *>(clang_type_system->GetNativePDBParser());
   if (ast_builder &&
       ast_builder->GetClangASTImporter().CanImport(compiler_type))
     return ast_builder->GetClangASTImporter().CompleteType(compiler_type);
   clang::QualType qt =
       clang::QualType::getFromOpaquePtr(compiler_type.GetOpaqueQualType());
 
   return ast_builder->CompleteType(qt);
 }
 
 void SymbolFileNativePDB::GetTypes(lldb_private::SymbolContextScope *sc_scope,
                                    TypeClass type_mask,
                                    lldb_private::TypeList &type_list) {}
 
 CompilerDeclContext
 SymbolFileNativePDB::FindNamespace(ConstString name,
                                    const CompilerDeclContext &parent_decl_ctx) {
   return {};
 }
 
-llvm::Expected<TypeSystem &>
+llvm::Expected<lldb::TypeSystemSP>
 SymbolFileNativePDB::GetTypeSystemForLanguage(lldb::LanguageType language) {
   auto type_system_or_err =
       m_objfile_sp->GetModule()->GetTypeSystemForLanguage(language);
-  if (type_system_or_err) {
-    type_system_or_err->SetSymbolFile(this);
-  }
+  if (type_system_or_err)
+    if (auto ts = *type_system_or_err)
+      ts->SetSymbolFile(this);
   return type_system_or_err;
 }
 
 uint64_t SymbolFileNativePDB::GetDebugInfoSize() {
   // PDB files are a separate file that contains all debug info.
   return m_index->pdb().getFileSize();
 }
 

lldb/source/Plugins/SymbolFile/PDB/PDBASTParser.cpp

GetBuiltinTypeForPDBEncodingAndBitSize(TypeSystemClang &clang_ast,
   case PDB_BuiltinType::Void:
     return clang_ast.GetBasicType(eBasicTypeVoid);
   case PDB_BuiltinType::Char:
     return clang_ast.GetBasicType(eBasicTypeChar);
   case PDB_BuiltinType::Bool:
     return clang_ast.GetBasicType(eBasicTypeBool);
   case PDB_BuiltinType::Long:
     if (width == ast.getTypeSize(ast.LongTy))
-      return CompilerType(&clang_ast, ast.LongTy.getAsOpaquePtr());
+      return CompilerType(clang_ast.weak_from_this(),
+                          ast.LongTy.getAsOpaquePtr());
     if (width == ast.getTypeSize(ast.LongLongTy))
-      return CompilerType(&clang_ast, ast.LongLongTy.getAsOpaquePtr());
+      return CompilerType(clang_ast.weak_from_this(),
+                          ast.LongLongTy.getAsOpaquePtr());
     break;
   case PDB_BuiltinType::ULong:
     if (width == ast.getTypeSize(ast.UnsignedLongTy))
-      return CompilerType(&clang_ast, ast.UnsignedLongTy.getAsOpaquePtr());
+      return CompilerType(clang_ast.weak_from_this(),
+                          ast.UnsignedLongTy.getAsOpaquePtr());
     if (width == ast.getTypeSize(ast.UnsignedLongLongTy))
-      return CompilerType(&clang_ast, ast.UnsignedLongLongTy.getAsOpaquePtr());
+      return CompilerType(clang_ast.weak_from_this(),
+                          ast.UnsignedLongLongTy.getAsOpaquePtr());
     break;
   case PDB_BuiltinType::WCharT:
     if (width == ast.getTypeSize(ast.WCharTy))
-      return CompilerType(&clang_ast, ast.WCharTy.getAsOpaquePtr());
+      return CompilerType(clang_ast.weak_from_this(),
+                          ast.WCharTy.getAsOpaquePtr());
     break;
   case PDB_BuiltinType::Char16:
-    return CompilerType(&clang_ast, ast.Char16Ty.getAsOpaquePtr());
+    return CompilerType(clang_ast.weak_from_this(),
+                        ast.Char16Ty.getAsOpaquePtr());
   case PDB_BuiltinType::Char32:
-    return CompilerType(&clang_ast, ast.Char32Ty.getAsOpaquePtr());
+    return CompilerType(clang_ast.weak_from_this(),
+                        ast.Char32Ty.getAsOpaquePtr());
   case PDB_BuiltinType::Float:
     // Note: types `long double` and `double` have same bit size in MSVC and
     // there is no information in the PDB to distinguish them. So when falling
     // back to default search, the compiler type of `long double` will be
     // represented by the one generated for `double`.
     break;
   }
   // If there is no match on PDB_BuiltinType, fall back to default search by

lldb/source/Plugins/SymbolFile/PDB/SymbolFilePDB.h

public:
 
   void FindTypesByRegex(const lldb_private::RegularExpression &regex,
                         uint32_t max_matches, lldb_private::TypeMap &types);
 
   void GetTypes(lldb_private::SymbolContextScope *sc_scope,
                 lldb::TypeClass type_mask,
                 lldb_private::TypeList &type_list) override;
 
-  llvm::Expected<lldb_private::TypeSystem &>
+  llvm::Expected<lldb::TypeSystemSP>
   GetTypeSystemForLanguage(lldb::LanguageType language) override;
 
   lldb_private::CompilerDeclContext FindNamespace(
       lldb_private::ConstString name,
       const lldb_private::CompilerDeclContext &parent_decl_ctx) override;
 
   llvm::StringRef GetPluginName() override { return GetPluginNameStatic(); }
 

lldb/source/Plugins/SymbolFile/PDB/SymbolFilePDB.cpp

SymbolFilePDB::ParseCompileUnitFunctionForPDBFunc(const PDBSymbolFunc &pdb_func,
   LanguageType lang = ParseLanguage(comp_unit);
   auto type_system_or_err = GetTypeSystemForLanguage(lang);
   if (auto err = type_system_or_err.takeError()) {
     LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
                    "Unable to parse PDBFunc");
     return nullptr;
   }
 
+  auto ts = *type_system_or_err;
   TypeSystemClang *clang_type_system =
-    llvm::dyn_cast_or_null<TypeSystemClang>(&type_system_or_err.get());
+    llvm::dyn_cast_or_null<TypeSystemClang>(ts.get());
   if (!clang_type_system)
     return nullptr;
   clang_type_system->GetPDBParser()->GetDeclForSymbol(pdb_func);
 
   return func_sp.get();
 }
 
 size_t SymbolFilePDB::ParseFunctions(CompileUnit &comp_unit) {
lldb_private::Type *SymbolFilePDB::ResolveTypeUID(lldb::user_id_t type_uid) {
   auto type_system_or_err =
       GetTypeSystemForLanguage(lldb::eLanguageTypeC_plus_plus);
   if (auto err = type_system_or_err.takeError()) {
     LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
                    "Unable to ResolveTypeUID");
     return nullptr;
   }
 
+  auto ts = *type_system_or_err;
   TypeSystemClang *clang_type_system =
-      llvm::dyn_cast_or_null<TypeSystemClang>(&type_system_or_err.get());
+      llvm::dyn_cast_or_null<TypeSystemClang>(ts.get());
   if (!clang_type_system)
     return nullptr;
   PDBASTParser *pdb = clang_type_system->GetPDBParser();
   if (!pdb)
     return nullptr;
 
   auto pdb_type = m_session_up->getSymbolById(type_uid);
   if (pdb_type == nullptr)
bool SymbolFilePDB::CompleteType(lldb_private::CompilerType &compiler_type) {
 
   auto type_system_or_err =
       GetTypeSystemForLanguage(lldb::eLanguageTypeC_plus_plus);
   if (auto err = type_system_or_err.takeError()) {
     LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
                    "Unable to get dynamic array info for UID");
     return false;
   }
-
+  auto ts = *type_system_or_err;
   TypeSystemClang *clang_ast_ctx =
-      llvm::dyn_cast_or_null<TypeSystemClang>(&type_system_or_err.get());
+      llvm::dyn_cast_or_null<TypeSystemClang>(ts.get());
 
   if (!clang_ast_ctx)
     return false;
 
   PDBASTParser *pdb = clang_ast_ctx->GetPDBParser();
   if (!pdb)
     return false;
 
   return pdb->CompleteTypeFromPDB(compiler_type);
 }
 
 lldb_private::CompilerDecl SymbolFilePDB::GetDeclForUID(lldb::user_id_t uid) {
   auto type_system_or_err =
       GetTypeSystemForLanguage(lldb::eLanguageTypeC_plus_plus);
   if (auto err = type_system_or_err.takeError()) {
     LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
                    "Unable to get decl for UID");
     return CompilerDecl();
   }
-
+  auto ts = *type_system_or_err;
   TypeSystemClang *clang_ast_ctx =
-      llvm::dyn_cast_or_null<TypeSystemClang>(&type_system_or_err.get());
+      llvm::dyn_cast_or_null<TypeSystemClang>(ts.get());
   if (!clang_ast_ctx)
     return CompilerDecl();
 
   PDBASTParser *pdb = clang_ast_ctx->GetPDBParser();
   if (!pdb)
     return CompilerDecl();
 
   auto symbol = m_session_up->getSymbolById(uid);
SymbolFilePDB::GetDeclContextForUID(lldb::user_id_t uid) {
   auto type_system_or_err =
       GetTypeSystemForLanguage(lldb::eLanguageTypeC_plus_plus);
   if (auto err = type_system_or_err.takeError()) {
     LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
                    "Unable to get DeclContext for UID");
     return CompilerDeclContext();
   }
 
+  auto ts = *type_system_or_err;
   TypeSystemClang *clang_ast_ctx =
-      llvm::dyn_cast_or_null<TypeSystemClang>(&type_system_or_err.get());
+      llvm::dyn_cast_or_null<TypeSystemClang>(ts.get());
   if (!clang_ast_ctx)
     return CompilerDeclContext();
 
   PDBASTParser *pdb = clang_ast_ctx->GetPDBParser();
   if (!pdb)
     return CompilerDeclContext();
 
   auto symbol = m_session_up->getSymbolById(uid);
SymbolFilePDB::GetDeclContextContainingUID(lldb::user_id_t uid) {
   auto type_system_or_err =
       GetTypeSystemForLanguage(lldb::eLanguageTypeC_plus_plus);
   if (auto err = type_system_or_err.takeError()) {
     LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
                    "Unable to get DeclContext containing UID");
     return CompilerDeclContext();
   }
 
+  auto ts = *type_system_or_err;
   TypeSystemClang *clang_ast_ctx =
-      llvm::dyn_cast_or_null<TypeSystemClang>(&type_system_or_err.get());
+      llvm::dyn_cast_or_null<TypeSystemClang>(ts.get());
   if (!clang_ast_ctx)
     return CompilerDeclContext();
 
   PDBASTParser *pdb = clang_ast_ctx->GetPDBParser();
   if (!pdb)
     return CompilerDeclContext();
 
   auto symbol = m_session_up->getSymbolById(uid);
void SymbolFilePDB::ParseDeclsForContext(
   auto type_system_or_err =
       GetTypeSystemForLanguage(lldb::eLanguageTypeC_plus_plus);
   if (auto err = type_system_or_err.takeError()) {
     LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
                    "Unable to parse decls for context");
     return;
   }
 
+  auto ts = *type_system_or_err;
   TypeSystemClang *clang_ast_ctx =
-      llvm::dyn_cast_or_null<TypeSystemClang>(&type_system_or_err.get());
+      llvm::dyn_cast_or_null<TypeSystemClang>(ts.get());
   if (!clang_ast_ctx)
     return;
 
   PDBASTParser *pdb = clang_ast_ctx->GetPDBParser();
   if (!pdb)
     return;
 
   pdb->ParseDeclsForDeclContext(
void SymbolFilePDB::DumpClangAST(Stream &s) {
   auto type_system_or_err =
       GetTypeSystemForLanguage(lldb::eLanguageTypeC_plus_plus);
   if (auto err = type_system_or_err.takeError()) {
     LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
                    "Unable to dump ClangAST");
     return;
   }
 
-  auto *clang_type_system =
-      llvm::dyn_cast_or_null<TypeSystemClang>(&type_system_or_err.get());
+  auto ts = *type_system_or_err;
+  TypeSystemClang *clang_type_system =
+      llvm::dyn_cast_or_null<TypeSystemClang>(ts.get());
   if (!clang_type_system)
     return;
   clang_type_system->Dump(s.AsRawOstream());
 }
 
 void SymbolFilePDB::FindTypesByRegex(
     const lldb_private::RegularExpression &regex, uint32_t max_matches,
     lldb_private::TypeMap &types) {
void SymbolFilePDB::GetTypes(lldb_private::SymbolContextScope *sc_scope,
   }
 
   for (auto type : type_collection) {
     type->GetForwardCompilerType();
     type_list.Insert(type->shared_from_this());
   }
 }
 
-llvm::Expected<lldb_private::TypeSystem &>
+llvm::Expected<lldb::TypeSystemSP>
 SymbolFilePDB::GetTypeSystemForLanguage(lldb::LanguageType language) {
   auto type_system_or_err =
       m_objfile_sp->GetModule()->GetTypeSystemForLanguage(language);
   if (type_system_or_err) {
-    type_system_or_err->SetSymbolFile(this);
+    if (auto ts = *type_system_or_err)
+      ts->SetSymbolFile(this);
   }
   return type_system_or_err;
 }
 
 PDBASTParser *SymbolFilePDB::GetPDBAstParser() {
   auto type_system_or_err =
       GetTypeSystemForLanguage(lldb::eLanguageTypeC_plus_plus);
   if (auto err = type_system_or_err.takeError()) {
     LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
                    "Unable to get PDB AST parser");
     return nullptr;
   }
 
+  auto ts = *type_system_or_err;
   auto *clang_type_system =
-      llvm::dyn_cast_or_null<TypeSystemClang>(&type_system_or_err.get());
+      llvm::dyn_cast_or_null<TypeSystemClang>(ts.get());
   if (!clang_type_system)
     return nullptr;
 
   return clang_type_system->GetPDBParser();
 }
 
 lldb_private::CompilerDeclContext
 SymbolFilePDB::FindNamespace(lldb_private::ConstString name,
                              const CompilerDeclContext &parent_decl_ctx) {
   std::lock_guard<std::recursive_mutex> guard(GetModuleMutex());
   auto type_system_or_err =
       GetTypeSystemForLanguage(lldb::eLanguageTypeC_plus_plus);
   if (auto err = type_system_or_err.takeError()) {
     LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
                    "Unable to find namespace {}", name.AsCString());
     return CompilerDeclContext();
   }
-
+  auto ts = *type_system_or_err;
   auto *clang_type_system =
-      llvm::dyn_cast_or_null<TypeSystemClang>(&type_system_or_err.get());
+      llvm::dyn_cast_or_null<TypeSystemClang>(ts.get());
   if (!clang_type_system)
     return CompilerDeclContext();
 
   PDBASTParser *pdb = clang_type_system->GetPDBParser();
   if (!pdb)
     return CompilerDeclContext();
 
   clang::DeclContext *decl_context = nullptr;
auto type_system_or_err = GetTypeSystemForLanguage(
       decl_ctx_type_system->GetMinimumLanguage(nullptr));
   if (auto err = type_system_or_err.takeError()) {
     LLDB_LOG_ERROR(
         GetLog(LLDBLog::Symbols), std::move(err),
         "Unable to determine if DeclContext matches this symbol file");
     return false;
   }
 
-  if (decl_ctx_type_system == &type_system_or_err.get())
+  if (decl_ctx_type_system == type_system_or_err->get())
     return true; // The type systems match, return true
 
   return false;
 }
 
 uint32_t SymbolFilePDB::GetCompilandId(const llvm::pdb::PDBSymbolData &data) {
   static const auto pred_upper = [](uint32_t lhs, SecContribInfo rhs) {
     return lhs < rhs.Offset;

lldb/source/Plugins/SystemRuntime/MacOSX/AppleGetItemInfoHandler.cpp

if (!m_get_item_info_impl_code) {
       }
 
       // Next make the runner function for our implementation utility function.
       auto type_system_or_err =
           thread.GetProcess()->GetTarget().GetScratchTypeSystemForLanguage(
               eLanguageTypeC);
       if (auto err = type_system_or_err.takeError()) {
         LLDB_LOG_ERROR(log, std::move(err),
-                       "Error inseting get-item-info function");
+                       "Error inserting get-item-info function");
         return args_addr;
       }
+      auto ts = *type_system_or_err;
+      if (!ts)
+        return args_addr;
+      
       CompilerType get_item_info_return_type =
-          type_system_or_err->GetBasicTypeFromAST(eBasicTypeVoid)
+          ts->GetBasicTypeFromAST(eBasicTypeVoid)
               .GetPointerType();
 
       Status error;
       get_item_info_caller = m_get_item_info_impl_code->MakeFunctionCaller(
           get_item_info_return_type, get_item_info_arglist,
           thread.shared_from_this(), error);
       if (error.Fail() || get_item_info_caller == nullptr) {
-        LLDB_LOGF(log, "Error Inserting get-item-info function: \"%s\".",
+        LLDB_LOGF(log, "Error inserting get-item-info function: \"%s\".",
                   error.AsCString());
         return args_addr;
       }
     } else {
       // If it's already made, then we can just retrieve the caller:
       get_item_info_caller = m_get_item_info_impl_code->GetFunctionCaller();
       if (!get_item_info_caller) {
         LLDB_LOGF(log, "Failed to get get-item-info introspection caller.");

lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.h

 //===-- TypeSystemClang.h ---------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLDB_SOURCE_PLUGINS_TYPESYSTEM_CLANG_TYPESYSTEMCLANG_H
 #define LLDB_SOURCE_PLUGINS_TYPESYSTEM_CLANG_TYPESYSTEMCLANG_H
 
 #include <cstdint>
 
 #include <functional>
 #include <initializer_list>
-#include <map>
 #include <memory>
 #include <set>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/ASTFwd.h"
public:
   ///         QualType's type pointer is a nullptr then the function returns an
   ///         invalid CompilerType.
   CompilerType GetType(clang::QualType qt) {
     if (qt.getTypePtrOrNull() == nullptr)
       return CompilerType();
     // Check that the type actually belongs to this TypeSystemClang.
     assert(qt->getAsTagDecl() == nullptr ||
            &qt->getAsTagDecl()->getASTContext() == &getASTContext());
-    return CompilerType(this, qt.getAsOpaquePtr());
+    return CompilerType(weak_from_this(), qt.getAsOpaquePtr());
   }
 
   CompilerType GetTypeForDecl(clang::NamedDecl *decl);
 
   CompilerType GetTypeForDecl(clang::TagDecl *decl);
 
   CompilerType GetTypeForDecl(clang::ObjCInterfaceDecl *objc_decl);
 
if (type_name.GetLength()) {
           ast.DeclarationNames.getIdentifier(&myIdent);
 
       clang::DeclContext::lookup_result result = decl_context->lookup(myName);
 
       if (!result.empty()) {
         clang::NamedDecl *named_decl = *result.begin();
         if (const RecordDeclType *record_decl =
                 llvm::dyn_cast<RecordDeclType>(named_decl))
-          compiler_type.SetCompilerType(
-              this, clang::QualType(record_decl->getTypeForDecl(), 0)
+          compiler_type =
+              CompilerType(weak_from_this(),
+                           clang::QualType(record_decl->getTypeForDecl(), 0)
                                .getAsOpaquePtr());
       }
     }
 
     return compiler_type;
   }
 
   CompilerType CreateStructForIdentifier(
       ConstString type_name,
private:
   std::unique_ptr<ClangASTSource> m_scratch_ast_source_up;
 
   // FIXME: GCC 5.x doesn't support enum as map keys.
   typedef int IsolatedASTKey;
 
   /// Map from IsolatedASTKind to their actual TypeSystemClang instance.
   /// This map is lazily filled with sub-ASTs and should be accessed via
   /// `GetSubAST` (which lazily fills this map).
-  std::unordered_map<IsolatedASTKey, std::unique_ptr<TypeSystemClang>>
+  llvm::DenseMap<IsolatedASTKey, std::shared_ptr<TypeSystemClang>>
       m_isolated_asts;
 };
 
 } // namespace lldb_private
 
 #endif // LLDB_SOURCE_PLUGINS_TYPESYSTEM_CLANG_TYPESYSTEMCLANG_H

lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp

-//===-- TypeSystemClang.cpp -----------------------------------------------===//
+//===-- TypeSystemClang.cpp -----------------------------------------------==='//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "TypeSystemClang.h"

 
 CompilerType TypeSystemClang::GetBasicType(lldb::BasicType basic_type) {
   clang::ASTContext &ast = getASTContext();
 
   lldb::opaque_compiler_type_t clang_type =
       GetOpaqueCompilerType(&ast, basic_type);
 
   if (clang_type)
-    return CompilerType(this, clang_type);
+    return CompilerType(weak_from_this(), clang_type);
   return CompilerType();
 }
 
 CompilerType TypeSystemClang::GetBuiltinTypeForDWARFEncodingAndBitSize(
     llvm::StringRef type_name, uint32_t dw_ate, uint32_t bit_size) {
   ASTContext &ast = getASTContext();
 
   switch (dw_ate) {
CompilerType TypeSystemClang::GetCStringType(bool is_const) {
   if (is_const)
     char_type.addConst();
 
   return GetType(ast.getPointerType(char_type));
 }
 
 bool TypeSystemClang::AreTypesSame(CompilerType type1, CompilerType type2,
                                    bool ignore_qualifiers) {
-  TypeSystemClang *ast =
-      llvm::dyn_cast_or_null<TypeSystemClang>(type1.GetTypeSystem());
-  if (!ast || ast != type2.GetTypeSystem())
+  auto ast = type1.GetTypeSystem().dyn_cast_or_null<TypeSystemClang>();
+  if (!ast || type1.GetTypeSystem() != type2.GetTypeSystem())
     return false;
 
   if (type1.GetOpaqueQualType() == type2.GetOpaqueQualType())
     return true;
 
   QualType type1_qual = ClangUtil::GetQualType(type1);
   QualType type2_qual = ClangUtil::GetQualType(type2);
 
bool TypeSystemClang::IsArrayType(lldb::opaque_compiler_type_t type,
   const clang::Type::TypeClass type_class = qual_type->getTypeClass();
   switch (type_class) {
   default:
     break;
 
   case clang::Type::ConstantArray:
     if (element_type_ptr)
       element_type_ptr->SetCompilerType(
-          this, llvm::cast<clang::ConstantArrayType>(qual_type)
+          weak_from_this(), llvm::cast<clang::ConstantArrayType>(qual_type)
                                 ->getElementType()
                                 .getAsOpaquePtr());
     if (size)
       *size = llvm::cast<clang::ConstantArrayType>(qual_type)
                   ->getSize()
                   .getLimitedValue(ULLONG_MAX);
     if (is_incomplete)
       *is_incomplete = false;
     return true;
 
   case clang::Type::IncompleteArray:
     if (element_type_ptr)
       element_type_ptr->SetCompilerType(
-          this, llvm::cast<clang::IncompleteArrayType>(qual_type)
+          weak_from_this(), llvm::cast<clang::IncompleteArrayType>(qual_type)
                                 ->getElementType()
                                 .getAsOpaquePtr());
     if (size)
       *size = 0;
     if (is_incomplete)
       *is_incomplete = true;
     return true;
 
   case clang::Type::VariableArray:
     if (element_type_ptr)
       element_type_ptr->SetCompilerType(
-          this, llvm::cast<clang::VariableArrayType>(qual_type)
+          weak_from_this(), llvm::cast<clang::VariableArrayType>(qual_type)
                                 ->getElementType()
                                 .getAsOpaquePtr());
     if (size)
       *size = 0;
     if (is_incomplete)
       *is_incomplete = false;
     return true;
 
   case clang::Type::DependentSizedArray:
     if (element_type_ptr)
       element_type_ptr->SetCompilerType(
-          this, llvm::cast<clang::DependentSizedArrayType>(qual_type)
-                    ->getElementType()
-                    .getAsOpaquePtr());
+          weak_from_this(),
+          llvm::cast<clang::DependentSizedArrayType>(qual_type)
     if (size)
       *size = 0;
     if (is_incomplete)
       *is_incomplete = false;
     return true;
   }
   if (element_type_ptr)
     element_type_ptr->Clear();
bool TypeSystemClang::IsVectorType(lldb::opaque_compiler_type_t type,
   case clang::Type::ExtVector: {
     const clang::ExtVectorType *ext_vector_type =
         qual_type->getAs<clang::ExtVectorType>();
     if (ext_vector_type) {
       if (size)
         *size = ext_vector_type->getNumElements();
       if (element_type)
         *element_type =
-            CompilerType(this, ext_vector_type->getElementType().getAsOpaquePtr());
+            CompilerType(weak_from_this(),
+                         ext_vector_type->getElementType().getAsOpaquePtr());
     }
     return true;
   }
   default:
     break;
   }
   return false;
 }
if (GetCompleteType(type)) {
                 if (field_qual_type.getTypePtr() != base_qual_type.getTypePtr())
                   return 0;
               }
             } else
               return 0;
             ++num_fields;
           }
           if (base_type_ptr)
-            *base_type_ptr = CompilerType(this, base_qual_type.getAsOpaquePtr());
+            *base_type_ptr =
+                CompilerType(weak_from_this(), base_qual_type.getAsOpaquePtr());
           return num_fields;
         }
       }
     }
     break;
 
   default:
     break;

 TypeSystemClang::GetFunctionArgumentAtIndex(lldb::opaque_compiler_type_t type,
                                             const size_t index) {
   if (type) {
     clang::QualType qual_type(GetQualType(type));
     const clang::FunctionProtoType *func =
         llvm::dyn_cast<clang::FunctionProtoType>(qual_type.getTypePtr());
     if (func) {
       if (index < func->getNumParams())
-        return CompilerType(this, func->getParamType(index).getAsOpaquePtr());
+        return CompilerType(weak_from_this(), func->getParamType(index).getAsOpaquePtr());
     }
   }
   return CompilerType();
 }
 
 bool TypeSystemClang::IsFunctionPointerType(lldb::opaque_compiler_type_t type) {
   if (type) {
     clang::QualType qual_type = RemoveWrappingTypes(GetCanonicalQualType(type));
if (type) {
     clang::QualType qual_type = RemoveWrappingTypes(GetCanonicalQualType(type));
 
     if (qual_type->isBlockPointerType()) {
       if (function_pointer_type_ptr) {
         const clang::BlockPointerType *block_pointer_type =
             qual_type->castAs<clang::BlockPointerType>();
         QualType pointee_type = block_pointer_type->getPointeeType();
         QualType function_pointer_type = m_ast_up->getPointerType(pointee_type);
-        *function_pointer_type_ptr =
-            CompilerType(this, function_pointer_type.getAsOpaquePtr());
+        *function_pointer_type_ptr = CompilerType(
+            weak_from_this(), function_pointer_type.getAsOpaquePtr());
       }
       return true;
     }
 
     const clang::Type::TypeClass type_class = qual_type->getTypeClass();
     switch (type_class) {
     default:
       break;
case clang::Type::Builtin:
       case clang::BuiltinType::ObjCId:
       case clang::BuiltinType::ObjCClass:
         return true;
       }
       return false;
     case clang::Type::ObjCObjectPointer:
       if (pointee_type)
         pointee_type->SetCompilerType(
-            this, llvm::cast<clang::ObjCObjectPointerType>(qual_type)
-                      ->getPointeeType()
-                      .getAsOpaquePtr());
+            weak_from_this(),
+            llvm::cast<clang::ObjCObjectPointerType>(qual_type)
       return true;
     case clang::Type::BlockPointer:
       if (pointee_type)
         pointee_type->SetCompilerType(
-            this, llvm::cast<clang::BlockPointerType>(qual_type)
+            weak_from_this(), llvm::cast<clang::BlockPointerType>(qual_type)
                                   ->getPointeeType()
                                   .getAsOpaquePtr());
       return true;
     case clang::Type::Pointer:
       if (pointee_type)
-        pointee_type->SetCompilerType(this,
+        pointee_type->SetCompilerType(weak_from_this(),
                                       llvm::cast<clang::PointerType>(qual_type)
                                           ->getPointeeType()
                                           .getAsOpaquePtr());
       return true;
     case clang::Type::MemberPointer:
       if (pointee_type)
         pointee_type->SetCompilerType(
-            this, llvm::cast<clang::MemberPointerType>(qual_type)
+            weak_from_this(), llvm::cast<clang::MemberPointerType>(qual_type)
                                   ->getPointeeType()
                                   .getAsOpaquePtr());
       return true;
     default:
       break;
     }
   }
   if (pointee_type)
     pointee_type->Clear();
   return false;
case clang::Type::Builtin:
       case clang::BuiltinType::ObjCId:
       case clang::BuiltinType::ObjCClass:
         return true;
       }
       return false;
     case clang::Type::ObjCObjectPointer:
       if (pointee_type)
         pointee_type->SetCompilerType(
-            this, llvm::cast<clang::ObjCObjectPointerType>(qual_type)
-                                 ->getPointeeType().getAsOpaquePtr());
+            weak_from_this(),
+            llvm::cast<clang::ObjCObjectPointerType>(qual_type)
+                ->getPointeeType()
+                .getAsOpaquePtr());
       return true;
     case clang::Type::BlockPointer:
       if (pointee_type)
         pointee_type->SetCompilerType(
-            this, llvm::cast<clang::BlockPointerType>(qual_type)
+            weak_from_this(), llvm::cast<clang::BlockPointerType>(qual_type)
                                   ->getPointeeType()
                                   .getAsOpaquePtr());
       return true;
     case clang::Type::Pointer:
       if (pointee_type)
-        pointee_type->SetCompilerType(this,
+        pointee_type->SetCompilerType(weak_from_this(),
                                       llvm::cast<clang::PointerType>(qual_type)
                                           ->getPointeeType()
                                           .getAsOpaquePtr());
       return true;
     case clang::Type::MemberPointer:
       if (pointee_type)
         pointee_type->SetCompilerType(
-            this, llvm::cast<clang::MemberPointerType>(qual_type)
+            weak_from_this(), llvm::cast<clang::MemberPointerType>(qual_type)
                                   ->getPointeeType()
                                   .getAsOpaquePtr());
       return true;
     case clang::Type::LValueReference:
       if (pointee_type)
         pointee_type->SetCompilerType(
-            this, llvm::cast<clang::LValueReferenceType>(qual_type)
+            weak_from_this(), llvm::cast<clang::LValueReferenceType>(qual_type)
                                   ->desugar()
                                   .getAsOpaquePtr());
       return true;
     case clang::Type::RValueReference:
       if (pointee_type)
         pointee_type->SetCompilerType(
-            this, llvm::cast<clang::RValueReferenceType>(qual_type)
+            weak_from_this(), llvm::cast<clang::RValueReferenceType>(qual_type)
                                   ->desugar()
                                   .getAsOpaquePtr());
       return true;
     default:
       break;
     }
   }
   if (pointee_type)
     pointee_type->Clear();
   return false;
 }
 
 bool TypeSystemClang::IsReferenceType(lldb::opaque_compiler_type_t type,
                                       CompilerType *pointee_type,
                                       bool *is_rvalue) {
   if (type) {
     clang::QualType qual_type = RemoveWrappingTypes(GetCanonicalQualType(type));
     const clang::Type::TypeClass type_class = qual_type->getTypeClass();
 
     switch (type_class) {
     case clang::Type::LValueReference:
       if (pointee_type)
         pointee_type->SetCompilerType(
-            this, llvm::cast<clang::LValueReferenceType>(qual_type)
+            weak_from_this(), llvm::cast<clang::LValueReferenceType>(qual_type)
                                   ->desugar()
                                   .getAsOpaquePtr());
       if (is_rvalue)
         *is_rvalue = false;
       return true;
     case clang::Type::RValueReference:
       if (pointee_type)
         pointee_type->SetCompilerType(
-            this, llvm::cast<clang::RValueReferenceType>(qual_type)
+            weak_from_this(), llvm::cast<clang::RValueReferenceType>(qual_type)
                                   ->desugar()
                                   .getAsOpaquePtr());
       if (is_rvalue)
         *is_rvalue = true;
       return true;
 
     default:
       break;
     }
   }
if (type) {
     bool success = false;
     const clang::Type::TypeClass type_class = qual_type->getTypeClass();
     switch (type_class) {
     case clang::Type::Builtin:
       if (check_objc &&
           llvm::cast<clang::BuiltinType>(qual_type)->getKind() ==
               clang::BuiltinType::ObjCId) {
         if (dynamic_pointee_type)
-          dynamic_pointee_type->SetCompilerType(this, type);
+          dynamic_pointee_type->SetCompilerType(weak_from_this(), type);
         return true;
       }
       break;
 
     case clang::Type::ObjCObjectPointer:
       if (check_objc) {
         if (const auto *objc_pointee_type =
                 qual_type->getPointeeType().getTypePtrOrNull()) {
           if (const auto *objc_object_type =
                   llvm::dyn_cast_or_null<clang::ObjCObjectType>(
                       objc_pointee_type)) {
             if (objc_object_type->isObjCClass())
               return false;
           }
         }
         if (dynamic_pointee_type)
           dynamic_pointee_type->SetCompilerType(
-              this, llvm::cast<clang::ObjCObjectPointerType>(qual_type)
-                        ->getPointeeType()
-                        .getAsOpaquePtr());
+              weak_from_this(),
+              llvm::cast<clang::ObjCObjectPointerType>(qual_type)
         return true;
       }
       break;
 
     case clang::Type::Pointer:
       pointee_qual_type =
           llvm::cast<clang::PointerType>(qual_type)->getPointeeType();
       success = true;
if (success) {
           pointee_qual_type.getCanonicalType()->getTypeClass();
       switch (pointee_type_class) {
       case clang::Type::Builtin:
         switch (llvm::cast<clang::BuiltinType>(pointee_qual_type)->getKind()) {
         case clang::BuiltinType::UnknownAny:
         case clang::BuiltinType::Void:
           if (dynamic_pointee_type)
             dynamic_pointee_type->SetCompilerType(
-                this, pointee_qual_type.getAsOpaquePtr());
+                weak_from_this(), pointee_qual_type.getAsOpaquePtr());
           return true;
         default:
           break;
         }
         break;
 
       case clang::Type::Record:
         if (check_cplusplus) {
if (success) {
                 else
                   success = false;
               }
             }
 
             if (success) {
               if (dynamic_pointee_type)
                 dynamic_pointee_type->SetCompilerType(
-                    this, pointee_qual_type.getAsOpaquePtr());
+                    weak_from_this(), pointee_qual_type.getAsOpaquePtr());
               return true;
             }
           }
         }
         break;
 
       case clang::Type::ObjCObject:
       case clang::Type::ObjCInterface:
         if (check_objc) {
           if (dynamic_pointee_type)
             dynamic_pointee_type->SetCompilerType(
-                this, pointee_qual_type.getAsOpaquePtr());
+                weak_from_this(), pointee_qual_type.getAsOpaquePtr());
           return true;
         }
         break;
 
       default:
         break;
       }
     }
const clang::BuiltinType *builtin_type =
         llvm::cast<clang::BuiltinType>(qual_type->getCanonicalTypeInternal());
 
     uint32_t builtin_type_flags = eTypeIsBuiltIn | eTypeHasValue;
     switch (builtin_type->getKind()) {
     case clang::BuiltinType::ObjCId:
     case clang::BuiltinType::ObjCClass:
       if (pointee_or_element_clang_type)
         pointee_or_element_clang_type->SetCompilerType(
-            this, getASTContext().ObjCBuiltinClassTy.getAsOpaquePtr());
+            weak_from_this(),
+            getASTContext().ObjCBuiltinClassTy.getAsOpaquePtr());
       builtin_type_flags |= eTypeIsPointer | eTypeIsObjC;
       break;
 
     case clang::BuiltinType::ObjCSel:
       if (pointee_or_element_clang_type)
         pointee_or_element_clang_type->SetCompilerType(
-            this, getASTContext().CharTy.getAsOpaquePtr());
+            weak_from_this(), getASTContext().CharTy.getAsOpaquePtr());
       builtin_type_flags |= eTypeIsPointer | eTypeIsObjC;
       break;
 
     case clang::BuiltinType::Bool:
     case clang::BuiltinType::Char_U:
     case clang::BuiltinType::UChar:
     case clang::BuiltinType::WChar_U:
     case clang::BuiltinType::Char16:
default:
       break;
     }
     return builtin_type_flags;
   }
 
   case clang::Type::BlockPointer:
     if (pointee_or_element_clang_type)
       pointee_or_element_clang_type->SetCompilerType(
-          this, qual_type->getPointeeType().getAsOpaquePtr());
+          weak_from_this(), qual_type->getPointeeType().getAsOpaquePtr());
     return eTypeIsPointer | eTypeHasChildren | eTypeIsBlock;
 
   case clang::Type::Complex: {
     uint32_t complex_type_flags =
         eTypeIsBuiltIn | eTypeHasValue | eTypeIsComplex;
     const clang::ComplexType *complex_type = llvm::dyn_cast<clang::ComplexType>(
         qual_type->getCanonicalTypeInternal());
     if (complex_type) {
       clang::QualType complex_element_type(complex_type->getElementType());
       if (complex_element_type->isIntegerType())
         complex_type_flags |= eTypeIsFloat;
       else if (complex_element_type->isFloatingType())
         complex_type_flags |= eTypeIsInteger;
     }
     return complex_type_flags;
   } break;
 
   case clang::Type::ConstantArray:
   case clang::Type::DependentSizedArray:
   case clang::Type::IncompleteArray:
   case clang::Type::VariableArray:
     if (pointee_or_element_clang_type)
       pointee_or_element_clang_type->SetCompilerType(
-          this, llvm::cast<clang::ArrayType>(qual_type.getTypePtr())
+          weak_from_this(), llvm::cast<clang::ArrayType>(qual_type.getTypePtr())
                                 ->getElementType()
                                 .getAsOpaquePtr());
     return eTypeHasChildren | eTypeIsArray;
 
   case clang::Type::DependentName:
     return 0;
   case clang::Type::DependentSizedExtVector:
     return eTypeHasChildren | eTypeIsVector;
   case clang::Type::DependentTemplateSpecialization:
     return eTypeIsTemplate;
 
   case clang::Type::Enum:
     if (pointee_or_element_clang_type)
       pointee_or_element_clang_type->SetCompilerType(
-          this, llvm::cast<clang::EnumType>(qual_type)
+          weak_from_this(), llvm::cast<clang::EnumType>(qual_type)
                                 ->getDecl()
                                 ->getIntegerType()
                                 .getAsOpaquePtr());
     return eTypeIsEnumeration | eTypeHasValue;
 
   case clang::Type::FunctionProto:
     return eTypeIsFuncPrototype | eTypeHasValue;
   case clang::Type::FunctionNoProto:
     return eTypeIsFuncPrototype | eTypeHasValue;
   case clang::Type::InjectedClassName:
     return 0;
 
   case clang::Type::LValueReference:
   case clang::Type::RValueReference:
     if (pointee_or_element_clang_type)
       pointee_or_element_clang_type->SetCompilerType(
-          this, llvm::cast<clang::ReferenceType>(qual_type.getTypePtr())
-                    ->getPointeeType()
-                    .getAsOpaquePtr());
+          weak_from_this(),
+          llvm::cast<clang::ReferenceType>(qual_type.getTypePtr())
     return eTypeHasChildren | eTypeIsReference | eTypeHasValue;
 
   case clang::Type::MemberPointer:
     return eTypeIsPointer | eTypeIsMember | eTypeHasValue;
 
   case clang::Type::ObjCObjectPointer:
     if (pointee_or_element_clang_type)
       pointee_or_element_clang_type->SetCompilerType(
-          this, qual_type->getPointeeType().getAsOpaquePtr());
+          weak_from_this(), qual_type->getPointeeType().getAsOpaquePtr());
     return eTypeHasChildren | eTypeIsObjC | eTypeIsClass | eTypeIsPointer |
            eTypeHasValue;
 
   case clang::Type::ObjCObject:
     return eTypeHasChildren | eTypeIsObjC | eTypeIsClass;
   case clang::Type::ObjCInterface:
     return eTypeHasChildren | eTypeIsObjC | eTypeIsClass;
 
   case clang::Type::Pointer:
     if (pointee_or_element_clang_type)
       pointee_or_element_clang_type->SetCompilerType(
-          this, qual_type->getPointeeType().getAsOpaquePtr());
+          weak_from_this(), qual_type->getPointeeType().getAsOpaquePtr());
     return eTypeHasChildren | eTypeIsPointer | eTypeHasValue;
 
   case clang::Type::Record:
     if (qual_type->getAsCXXRecordDecl())
       return eTypeHasChildren | eTypeIsClass | eTypeIsCPlusPlus;
     else
       return eTypeHasChildren | eTypeIsStructUnion;
     break;
const clang::ObjCInterfaceType *objc_interface_type =
         objc_class_type->getInterfaceType();
     if (objc_interface_type &&
         GetCompleteType(static_cast<lldb::opaque_compiler_type_t>(
             const_cast<clang::ObjCInterfaceType *>(objc_interface_type)))) {
       clang::ObjCInterfaceDecl *class_interface_decl =
           objc_interface_type->getDecl();
       if (class_interface_decl) {
         return CompilerType(
-            this, GetObjCFieldAtIndex(&getASTContext(), class_interface_decl,
-                                      idx, name, bit_offset_ptr,
-                                      bitfield_bit_size_ptr, is_bitfield_ptr));
+            weak_from_this(),
+            GetObjCFieldAtIndex(&getASTContext(), class_interface_decl, idx,
+                                name, bit_offset_ptr, bitfield_bit_size_ptr,
+                                is_bitfield_ptr));
       }
     }
     break;
   }
 
   case clang::Type::ObjCObject:
   case clang::Type::ObjCInterface:
     if (GetCompleteType(type)) {
       const clang::ObjCObjectType *objc_class_type =
           llvm::dyn_cast<clang::ObjCObjectType>(qual_type.getTypePtr());
       assert(objc_class_type);
       if (objc_class_type) {
         clang::ObjCInterfaceDecl *class_interface_decl =
             objc_class_type->getInterface();
         return CompilerType(
-            this, GetObjCFieldAtIndex(&getASTContext(), class_interface_decl,
-                                      idx, name, bit_offset_ptr,
-                                      bitfield_bit_size_ptr, is_bitfield_ptr));
+            weak_from_this(),
+            GetObjCFieldAtIndex(&getASTContext(), class_interface_decl, idx,
+                                name, bit_offset_ptr, bitfield_bit_size_ptr,
+                                is_bitfield_ptr));
       }
     }
     break;
 
   default:
     break;
   }
   return CompilerType();
TypeSystemClang::GetIntegralTemplateArgument(lldb::opaque_compiler_type_t type,
   if (!arg || arg->getKind() != clang::TemplateArgument::Integral)
     return llvm::None;
 
   return {{arg->getAsIntegral(), GetType(arg->getIntegralType())}};
 }
 
 CompilerType TypeSystemClang::GetTypeForFormatters(void *type) {
   if (type)
-    return ClangUtil::RemoveFastQualifiers(CompilerType(this, type));
+    return ClangUtil::RemoveFastQualifiers(CompilerType(weak_from_this(), type));
   return CompilerType();
 }
 
 clang::EnumDecl *TypeSystemClang::GetAsEnumDecl(const CompilerType &type) {
   const clang::EnumType *enutype =
       llvm::dyn_cast<clang::EnumType>(ClangUtil::GetCanonicalQualType(type));
   if (enutype)
     return enutype->getDecl();

 }
 
 clang::FieldDecl *TypeSystemClang::AddFieldToRecordType(
     const CompilerType &type, llvm::StringRef name,
     const CompilerType &field_clang_type, AccessType access,
     uint32_t bitfield_bit_size) {
   if (!type.IsValid() || !field_clang_type.IsValid())
     return nullptr;
-  TypeSystemClang *ast =
-      llvm::dyn_cast_or_null<TypeSystemClang>(type.GetTypeSystem());
+  auto ts = type.GetTypeSystem();
+  auto ast = ts.dyn_cast_or_null<TypeSystemClang>();
   if (!ast)
     return nullptr;
   clang::ASTContext &clang_ast = ast->getASTContext();
   clang::IdentifierInfo *ident = nullptr;
   if (!name.empty())
     ident = &clang_ast.Idents.get(name);
 
   clang::FieldDecl *field = nullptr;
clang::FieldDecl *TypeSystemClang::AddFieldToRecordType(
   }
   return field;
 }
 
 void TypeSystemClang::BuildIndirectFields(const CompilerType &type) {
   if (!type)
     return;
 
-  TypeSystemClang *ast = llvm::dyn_cast<TypeSystemClang>(type.GetTypeSystem());
+  auto ts = type.GetTypeSystem();
+  auto ast = ts.dyn_cast_or_null<TypeSystemClang>();
   if (!ast)
     return;
 
   clang::RecordDecl *record_decl = ast->GetAsRecordDecl(type);
 
   if (!record_decl)
     return;
 
for (IndirectFieldVector::iterator ifi = indirect_fields.begin(),
                                      ife = indirect_fields.end();
        ifi < ife; ++ifi) {
     record_decl->addDecl(*ifi);
   }
 }
 
 void TypeSystemClang::SetIsPacked(const CompilerType &type) {
   if (type) {
-    TypeSystemClang *ast =
-        llvm::dyn_cast<TypeSystemClang>(type.GetTypeSystem());
+    auto ts = type.GetTypeSystem();
+    auto ast = ts.dyn_cast_or_null<TypeSystemClang>();
     if (ast) {
       clang::RecordDecl *record_decl = GetAsRecordDecl(type);
 
       if (!record_decl)
         return;
 
       record_decl->addAttr(
           clang::PackedAttr::CreateImplicit(ast->getASTContext()));
     }
   }
 }
 
 clang::VarDecl *TypeSystemClang::AddVariableToRecordType(
     const CompilerType &type, llvm::StringRef name,
     const CompilerType &var_type, AccessType access) {
   if (!type.IsValid() || !var_type.IsValid())
     return nullptr;
 
-  TypeSystemClang *ast = llvm::dyn_cast<TypeSystemClang>(type.GetTypeSystem());
+  auto ts = type.GetTypeSystem();
+  auto ast = ts.dyn_cast_or_null<TypeSystemClang>();
   if (!ast)
     return nullptr;
 
   clang::RecordDecl *record_decl = ast->GetAsRecordDecl(type);
   if (!record_decl)
     return nullptr;
 
   clang::VarDecl *var_decl = nullptr;
bool TypeSystemClang::TransferBaseClasses(
   for (auto &b : bases)
     raw_bases.push_back(b.get());
   cxx_record_decl->setBases(raw_bases.data(), raw_bases.size());
   return true;
 }
 
 bool TypeSystemClang::SetObjCSuperClass(
     const CompilerType &type, const CompilerType &superclass_clang_type) {
-  TypeSystemClang *ast =
-      llvm::dyn_cast_or_null<TypeSystemClang>(type.GetTypeSystem());
+  auto ts = type.GetTypeSystem();
+  auto ast = ts.dyn_cast_or_null<TypeSystemClang>();
   if (!ast)
     return false;
   clang::ASTContext &clang_ast = ast->getASTContext();
 
   if (type && superclass_clang_type.IsValid() &&
       superclass_clang_type.GetTypeSystem() == type.GetTypeSystem()) {
     clang::ObjCInterfaceDecl *class_interface_decl =
         GetAsObjCInterfaceDecl(type);

 bool TypeSystemClang::AddObjCClassProperty(
     const CompilerType &type, const char *property_name,
     const CompilerType &property_clang_type, clang::ObjCIvarDecl *ivar_decl,
     const char *property_setter_name, const char *property_getter_name,
     uint32_t property_attributes, ClangASTMetadata *metadata) {
   if (!type || !property_clang_type.IsValid() || property_name == nullptr ||
       property_name[0] == '\0')
     return false;
-  TypeSystemClang *ast = llvm::dyn_cast<TypeSystemClang>(type.GetTypeSystem());
+  auto ts = type.GetTypeSystem();
+  auto ast = ts.dyn_cast_or_null<TypeSystemClang>();
   if (!ast)
     return false;
   clang::ASTContext &clang_ast = ast->getASTContext();
 
   clang::ObjCInterfaceDecl *class_interface_decl = GetAsObjCInterfaceDecl(type);
   if (!class_interface_decl)
     return false;
 
clang::ObjCMethodDecl *TypeSystemClang::AddMethodToObjCObjectType(
     bool is_artificial, bool is_variadic, bool is_objc_direct_call) {
   if (!type || !method_clang_type.IsValid())
     return nullptr;
 
   clang::ObjCInterfaceDecl *class_interface_decl = GetAsObjCInterfaceDecl(type);
 
   if (class_interface_decl == nullptr)
     return nullptr;
-  TypeSystemClang *lldb_ast =
-      llvm::dyn_cast<TypeSystemClang>(type.GetTypeSystem());
+  auto ts = type.GetTypeSystem();
+  auto lldb_ast = ts.dyn_cast_or_null<TypeSystemClang>();
   if (lldb_ast == nullptr)
     return nullptr;
   clang::ASTContext &ast = lldb_ast->getASTContext();
 
   const char *selector_start = ::strchr(name, ' ');
   if (selector_start == nullptr)
     return nullptr;
 

 }
 
 bool TypeSystemClang::CompleteTagDeclarationDefinition(
     const CompilerType &type) {
   clang::QualType qual_type(ClangUtil::GetQualType(type));
   if (qual_type.isNull())
     return false;
 
-  TypeSystemClang *lldb_ast =
-      llvm::dyn_cast<TypeSystemClang>(type.GetTypeSystem());
+  auto ts = type.GetTypeSystem();
+  auto lldb_ast = ts.dyn_cast_or_null<TypeSystemClang>();
   if (lldb_ast == nullptr)
     return false;
 
   // Make sure we use the same methodology as
   // TypeSystemClang::StartTagDeclarationDefinition() as to how we start/end
   // the definition.
   const clang::TagType *tag_type = qual_type->getAs<clang::TagType>();
   if (tag_type) {

 
 clang::EnumConstantDecl *TypeSystemClang::AddEnumerationValueToEnumerationType(
     const CompilerType &enum_type, const Declaration &decl, const char *name,
     const llvm::APSInt &value) {
 
   if (!enum_type || ConstString(name).IsEmpty())
     return nullptr;
 
-  lldbassert(enum_type.GetTypeSystem() == static_cast<TypeSystem *>(this));
+  lldbassert(enum_type.GetTypeSystem().GetSharedPointer().get() ==
+             static_cast<TypeSystem *>(this));
 
   lldb::opaque_compiler_type_t enum_opaque_compiler_type =
       enum_type.GetOpaqueQualType();
 
   if (!enum_opaque_compiler_type)
     return nullptr;
 
   clang::QualType enum_qual_type(
CompilerType TypeSystemClang::GetEnumerationIntegerType(CompilerType type) {
   return GetType(enum_type->getDecl()->getIntegerType());
 }
 
 CompilerType
 TypeSystemClang::CreateMemberPointerType(const CompilerType &type,
                                          const CompilerType &pointee_type) {
   if (type && pointee_type.IsValid() &&
       type.GetTypeSystem() == pointee_type.GetTypeSystem()) {
-    TypeSystemClang *ast =
-        llvm::dyn_cast<TypeSystemClang>(type.GetTypeSystem());
+    auto ts = type.GetTypeSystem();
+    auto ast = ts.dyn_cast_or_null<TypeSystemClang>();
     if (!ast)
       return CompilerType();
     return ast->GetType(ast->getASTContext().getMemberPointerType(
         ClangUtil::GetQualType(pointee_type),
         ClangUtil::GetQualType(type).getTypePtr()));
   }
   return CompilerType();
 }
void TypeSystemClang::DumpSummary(lldb::opaque_compiler_type_t type,
   }
 }
 
 void TypeSystemClang::DumpTypeDescription(lldb::opaque_compiler_type_t type,
                                           lldb::DescriptionLevel level) {
   StreamFile s(stdout, false);
   DumpTypeDescription(type, &s, level);
 
-  CompilerType ct(this, type);
+  CompilerType ct(weak_from_this(), type);
   const clang::Type *clang_type = ClangUtil::GetQualType(ct).getTypePtr();
   ClangASTMetadata *metadata = GetMetadata(clang_type);
   if (metadata) {
     metadata->Dump(&s);
   }
 }
 
 void TypeSystemClang::DumpTypeDescription(lldb::opaque_compiler_type_t type,
void TypeSystemClang::RequireCompleteType(CompilerType type) {
   // it is not _really_ complete so we can later search for a definition in a
   // different module.
   // Since we provide layout assistance, layouts of types containing this class
   // will be correct even if we  are not able to find the definition elsewhere.
   bool started = TypeSystemClang::StartTagDeclarationDefinition(type);
   lldbassert(started && "Unable to start a class type definition.");
   TypeSystemClang::CompleteTagDeclarationDefinition(type);
   const clang::TagDecl *td = ClangUtil::GetAsTagDecl(type);
-  auto &ts = llvm::cast<TypeSystemClang>(*type.GetTypeSystem());
-  ts.GetMetadata(td)->SetIsForcefullyCompleted();
+  auto ts = type.GetTypeSystem().dyn_cast_or_null<TypeSystemClang>();
+  if (ts)
+    ts->GetMetadata(td)->SetIsForcefullyCompleted();
 }
 
 namespace {
 /// A specialized scratch AST used within ScratchTypeSystemClang.
 /// These are the ASTs backing the different IsolatedASTKinds. They behave
 /// like a normal ScratchTypeSystemClang but they don't own their own
 /// persistent  storage or target reference.
 class SpecializedScratchAST : public TypeSystemClang {
ScratchTypeSystemClang::GetForTarget(Target &target,
                                      bool create_on_demand) {
   auto type_system_or_err = target.GetScratchTypeSystemForLanguage(
       lldb::eLanguageTypeC, create_on_demand);
   if (auto err = type_system_or_err.takeError()) {
     LLDB_LOG_ERROR(GetLog(LLDBLog::Target), std::move(err),
                    "Couldn't get scratch TypeSystemClang");
     return nullptr;
   }
-  ScratchTypeSystemClang &scratch_ast =
-      llvm::cast<ScratchTypeSystemClang>(type_system_or_err.get());
+  auto ts = *type_system_or_err;
+  ScratchTypeSystemClang *scratch_ast =
+      llvm::dyn_cast_or_null<ScratchTypeSystemClang>(ts.get());
+  if (!scratch_ast)
+    return nullptr;
   // If no dedicated sub-AST was requested, just return the main AST.
   if (ast_kind == DefaultAST)
-    return &scratch_ast;
+    return scratch_ast;
   // Search the sub-ASTs.
-  return &scratch_ast.GetIsolatedAST(*ast_kind);
+  return &scratch_ast->GetIsolatedAST(*ast_kind);
 }
 
 /// Returns a human-readable name that uniquely identifiers the sub-AST kind.
 static llvm::StringRef
 GetNameForIsolatedASTKind(ScratchTypeSystemClang::IsolatedASTKind kind) {
   switch (kind) {
   case ScratchTypeSystemClang::IsolatedASTKind::CppModules:
     return "C++ modules";

 
 TypeSystemClang &ScratchTypeSystemClang::GetIsolatedAST(
     ScratchTypeSystemClang::IsolatedASTKind feature) {
   auto found_ast = m_isolated_asts.find(feature);
   if (found_ast != m_isolated_asts.end())
     return *found_ast->second;
 
   // Couldn't find the requested sub-AST, so create it now.
-  std::unique_ptr<TypeSystemClang> new_ast;
-  new_ast.reset(new SpecializedScratchAST(GetSpecializedASTName(feature),
-                                          m_triple, CreateASTSource()));
-  m_isolated_asts[feature] = std::move(new_ast);
-  return *m_isolated_asts[feature];
+  std::shared_ptr<TypeSystemClang> new_ast_sp =
+      std::make_shared<SpecializedScratchAST>(GetSpecializedASTName(feature),
+                                              m_triple, CreateASTSource());
+  m_isolated_asts.insert({feature, new_ast_sp});
+  return *new_ast_sp;
 }

lldb/source/Symbol/CompilerType.cpp

 
 using namespace lldb;
 using namespace lldb_private;
 
 // Tests
 
 bool CompilerType::IsAggregateType() const {
   if (IsValid())
-    return m_type_system->IsAggregateType(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsAggregateType(m_type);
   return false;
 }
 
 bool CompilerType::IsAnonymousType() const {
   if (IsValid())
-    return m_type_system->IsAnonymousType(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsAnonymousType(m_type);
   return false;
 }
 
 bool CompilerType::IsScopedEnumerationType() const {
   if (IsValid())
-    return m_type_system->IsScopedEnumerationType(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsScopedEnumerationType(m_type);
   return false;
 }
 
 bool CompilerType::IsArrayType(CompilerType *element_type_ptr, uint64_t *size,
                                bool *is_incomplete) const {
   if (IsValid())
-    return m_type_system->IsArrayType(m_type, element_type_ptr, size,
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsArrayType(m_type, element_type_ptr, size,
                                       is_incomplete);
 
   if (element_type_ptr)
     element_type_ptr->Clear();
   if (size)
     *size = 0;
   if (is_incomplete)
     *is_incomplete = false;
   return false;
 }
 
 bool CompilerType::IsVectorType(CompilerType *element_type,
                                 uint64_t *size) const {
   if (IsValid())
-    return m_type_system->IsVectorType(m_type, element_type, size);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsVectorType(m_type, element_type, size);
   return false;
 }
 
 bool CompilerType::IsRuntimeGeneratedType() const {
   if (IsValid())
-    return m_type_system->IsRuntimeGeneratedType(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsRuntimeGeneratedType(m_type);
   return false;
 }
 
 bool CompilerType::IsCharType() const {
   if (IsValid())
-    return m_type_system->IsCharType(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsCharType(m_type);
   return false;
 }
 
 bool CompilerType::IsCompleteType() const {
   if (IsValid())
-    return m_type_system->IsCompleteType(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsCompleteType(m_type);
   return false;
 }
 
 bool CompilerType::IsConst() const {
   if (IsValid())
-    return m_type_system->IsConst(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsConst(m_type);
   return false;
 }
 
 bool CompilerType::IsCStringType(uint32_t &length) const {
   if (IsValid())
-    return m_type_system->IsCStringType(m_type, length);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsCStringType(m_type, length);
   return false;
 }
 
 bool CompilerType::IsFunctionType() const {
   if (IsValid())
-    return m_type_system->IsFunctionType(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsFunctionType(m_type);
   return false;
 }
 
 // Used to detect "Homogeneous Floating-point Aggregates"
 uint32_t
 CompilerType::IsHomogeneousAggregate(CompilerType *base_type_ptr) const {
   if (IsValid())
-    return m_type_system->IsHomogeneousAggregate(m_type, base_type_ptr);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsHomogeneousAggregate(m_type, base_type_ptr);
   return 0;
 }
 
 size_t CompilerType::GetNumberOfFunctionArguments() const {
   if (IsValid())
-    return m_type_system->GetNumberOfFunctionArguments(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetNumberOfFunctionArguments(m_type);
   return 0;
 }
 
 CompilerType
 CompilerType::GetFunctionArgumentAtIndex(const size_t index) const {
   if (IsValid())
-    return m_type_system->GetFunctionArgumentAtIndex(m_type, index);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetFunctionArgumentAtIndex(m_type, index);
   return CompilerType();
 }
 
 bool CompilerType::IsFunctionPointerType() const {
   if (IsValid())
-    return m_type_system->IsFunctionPointerType(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsFunctionPointerType(m_type);
   return false;
 }
 
 bool CompilerType::IsBlockPointerType(
     CompilerType *function_pointer_type_ptr) const {
   if (IsValid())
-    return m_type_system->IsBlockPointerType(m_type, function_pointer_type_ptr);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsBlockPointerType(m_type, function_pointer_type_ptr);
   return false;
 }
 
 bool CompilerType::IsIntegerType(bool &is_signed) const {
   if (IsValid())
-    return m_type_system->IsIntegerType(m_type, is_signed);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsIntegerType(m_type, is_signed);
   return false;
 }
 
 bool CompilerType::IsEnumerationType(bool &is_signed) const {
   if (IsValid())
-    return m_type_system->IsEnumerationType(m_type, is_signed);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsEnumerationType(m_type, is_signed);
   return false;
 }
 
 bool CompilerType::IsIntegerOrEnumerationType(bool &is_signed) const {
   return IsIntegerType(is_signed) || IsEnumerationType(is_signed);
 }
 
 bool CompilerType::IsPointerType(CompilerType *pointee_type) const {
   if (IsValid()) {
-    return m_type_system->IsPointerType(m_type, pointee_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsPointerType(m_type, pointee_type);
   }
   if (pointee_type)
     pointee_type->Clear();
   return false;
 }
 
 bool CompilerType::IsPointerOrReferenceType(CompilerType *pointee_type) const {
   if (IsValid()) {
-    return m_type_system->IsPointerOrReferenceType(m_type, pointee_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsPointerOrReferenceType(m_type, pointee_type);
   }
   if (pointee_type)
     pointee_type->Clear();
   return false;
 }
 
 bool CompilerType::IsReferenceType(CompilerType *pointee_type,
                                    bool *is_rvalue) const {
   if (IsValid()) {
-    return m_type_system->IsReferenceType(m_type, pointee_type, is_rvalue);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsReferenceType(m_type, pointee_type, is_rvalue);
   }
   if (pointee_type)
     pointee_type->Clear();
   return false;
 }
 
 bool CompilerType::ShouldTreatScalarValueAsAddress() const {
   if (IsValid())
-    return m_type_system->ShouldTreatScalarValueAsAddress(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->ShouldTreatScalarValueAsAddress(m_type);
   return false;
 }
 
 bool CompilerType::IsFloatingPointType(uint32_t &count,
                                        bool &is_complex) const {
   if (IsValid()) {
-    return m_type_system->IsFloatingPointType(m_type, count, is_complex);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsFloatingPointType(m_type, count, is_complex);
   }
   count = 0;
   is_complex = false;
   return false;
 }
 
 bool CompilerType::IsDefined() const {
   if (IsValid())
-    return m_type_system->IsDefined(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsDefined(m_type);
   return true;
 }
 
 bool CompilerType::IsPolymorphicClass() const {
   if (IsValid()) {
-    return m_type_system->IsPolymorphicClass(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsPolymorphicClass(m_type);
   }
   return false;
 }
 
 bool CompilerType::IsPossibleDynamicType(CompilerType *dynamic_pointee_type,
                                          bool check_cplusplus,
                                          bool check_objc) const {
   if (IsValid())
-    return m_type_system->IsPossibleDynamicType(m_type, dynamic_pointee_type,
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsPossibleDynamicType(m_type, dynamic_pointee_type,
                                                 check_cplusplus, check_objc);
   return false;
 }
 
 bool CompilerType::IsScalarType() const {
-  if (!IsValid())
-    return false;
-
-  return m_type_system->IsScalarType(m_type);
+  if (IsValid())
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsScalarType(m_type);
 }
 
 bool CompilerType::IsTypedefType() const {
-  if (!IsValid())
-    return false;
-  return m_type_system->IsTypedefType(m_type);
+  if (IsValid())
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsTypedefType(m_type);
 }
 
 bool CompilerType::IsVoidType() const {
-  if (!IsValid())
-    return false;
-  return m_type_system->IsVoidType(m_type);
+  if (IsValid())
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsVoidType(m_type);
 }
 
 bool CompilerType::IsPointerToScalarType() const {
   if (!IsValid())
     return false;
 
   return IsPointerType() && GetPointeeType().IsScalarType();
 }
 
 bool CompilerType::IsArrayOfScalarType() const {
   CompilerType element_type;
   if (IsArrayType(&element_type))
     return element_type.IsScalarType();
   return false;
 }
 
 bool CompilerType::IsBeingDefined() const {
-  if (!IsValid())
-    return false;
-  return m_type_system->IsBeingDefined(m_type);
+  if (IsValid())
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsBeingDefined(m_type);
 }
 
 // Type Completion
 
 bool CompilerType::GetCompleteType() const {
-  if (!IsValid())
-    return false;
-  return m_type_system->GetCompleteType(m_type);
+  if (IsValid())
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetCompleteType(m_type);
 }
 
 // AST related queries
 size_t CompilerType::GetPointerByteSize() const {
-  if (m_type_system)
-    return m_type_system->GetPointerByteSize();
+  if (auto type_system_sp = GetTypeSystem())
+    return type_system_sp->GetPointerByteSize();
   return 0;
 }
 
 ConstString CompilerType::GetTypeName(bool BaseOnly) const {
   if (IsValid()) {
-    return m_type_system->GetTypeName(m_type, BaseOnly);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetTypeName(m_type, BaseOnly);
   }
   return ConstString("<invalid>");
 }
 
 ConstString CompilerType::GetDisplayTypeName() const {
   if (IsValid())
-    return m_type_system->GetDisplayTypeName(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetDisplayTypeName(m_type);
   return ConstString("<invalid>");
 }
 
 uint32_t CompilerType::GetTypeInfo(
     CompilerType *pointee_or_element_compiler_type) const {
-  if (!IsValid())
-    return 0;
-
-  return m_type_system->GetTypeInfo(m_type, pointee_or_element_compiler_type);
+  if (IsValid())
+  if (auto type_system_sp = GetTypeSystem())
+    return type_system_sp->GetTypeInfo(m_type,
+                                       pointee_or_element_compiler_type);
 }
 
 lldb::LanguageType CompilerType::GetMinimumLanguage() {
-  if (!IsValid())
-    return lldb::eLanguageTypeC;
-
-  return m_type_system->GetMinimumLanguage(m_type);
+  if (IsValid())
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetMinimumLanguage(m_type);
 }
 
 lldb::TypeClass CompilerType::GetTypeClass() const {
-  if (!IsValid())
-    return lldb::eTypeClassInvalid;
-
-  return m_type_system->GetTypeClass(m_type);
+  if (IsValid())
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetTypeClass(m_type);
 }
 
-void CompilerType::SetCompilerType(TypeSystem *type_system,
+void CompilerType::SetCompilerType(lldb::TypeSystemWP type_system,
                                    lldb::opaque_compiler_type_t type) {
   m_type_system = type_system;
   m_type = type;
 }
 
+void CompilerType::SetCompilerType(CompilerType::TypeSystemSPWrapper type_system,
+                                   lldb::opaque_compiler_type_t type) {
+  m_type_system = type_system.GetSharedPointer();
+  m_type = type;
+}
+
 unsigned CompilerType::GetTypeQualifiers() const {
   if (IsValid())
-    return m_type_system->GetTypeQualifiers(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetTypeQualifiers(m_type);
   return 0;
 }
 
 // Creating related types
 
 CompilerType
 CompilerType::GetArrayElementType(ExecutionContextScope *exe_scope) const {
   if (IsValid()) {
-    return m_type_system->GetArrayElementType(m_type, exe_scope);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetArrayElementType(m_type, exe_scope);
   }
   return CompilerType();
 }
 
 CompilerType CompilerType::GetArrayType(uint64_t size) const {
   if (IsValid()) {
-    return m_type_system->GetArrayType(m_type, size);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetArrayType(m_type, size);
   }
   return CompilerType();
 }
 
 CompilerType CompilerType::GetCanonicalType() const {
   if (IsValid())
-    return m_type_system->GetCanonicalType(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetCanonicalType(m_type);
   return CompilerType();
 }
 
 CompilerType CompilerType::GetFullyUnqualifiedType() const {
   if (IsValid())
-    return m_type_system->GetFullyUnqualifiedType(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetFullyUnqualifiedType(m_type);
   return CompilerType();
 }
 
 CompilerType CompilerType::GetEnumerationIntegerType() const {
   if (IsValid())
-    return m_type_system->GetEnumerationIntegerType(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetEnumerationIntegerType(m_type);
   return CompilerType();
 }
 
 int CompilerType::GetFunctionArgumentCount() const {
   if (IsValid()) {
-    return m_type_system->GetFunctionArgumentCount(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetFunctionArgumentCount(m_type);
   }
   return -1;
 }
 
 CompilerType CompilerType::GetFunctionArgumentTypeAtIndex(size_t idx) const {
   if (IsValid()) {
-    return m_type_system->GetFunctionArgumentTypeAtIndex(m_type, idx);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetFunctionArgumentTypeAtIndex(m_type, idx);
   }
   return CompilerType();
 }
 
 CompilerType CompilerType::GetFunctionReturnType() const {
   if (IsValid()) {
-    return m_type_system->GetFunctionReturnType(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetFunctionReturnType(m_type);
   }
   return CompilerType();
 }
 
 size_t CompilerType::GetNumMemberFunctions() const {
   if (IsValid()) {
-    return m_type_system->GetNumMemberFunctions(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetNumMemberFunctions(m_type);
   }
   return 0;
 }
 
 TypeMemberFunctionImpl CompilerType::GetMemberFunctionAtIndex(size_t idx) {
   if (IsValid()) {
-    return m_type_system->GetMemberFunctionAtIndex(m_type, idx);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetMemberFunctionAtIndex(m_type, idx);
   }
   return TypeMemberFunctionImpl();
 }
 
 CompilerType CompilerType::GetNonReferenceType() const {
   if (IsValid())
-    return m_type_system->GetNonReferenceType(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetNonReferenceType(m_type);
   return CompilerType();
 }
 
 CompilerType CompilerType::GetPointeeType() const {
   if (IsValid()) {
-    return m_type_system->GetPointeeType(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetPointeeType(m_type);
   }
   return CompilerType();
 }
 
 CompilerType CompilerType::GetPointerType() const {
   if (IsValid()) {
-    return m_type_system->GetPointerType(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetPointerType(m_type);
   }
   return CompilerType();
 }
 
 CompilerType CompilerType::GetLValueReferenceType() const {
   if (IsValid())
-    return m_type_system->GetLValueReferenceType(m_type);
-  else
-    return CompilerType();
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetLValueReferenceType(m_type);
 }
 
 CompilerType CompilerType::GetRValueReferenceType() const {
   if (IsValid())
-    return m_type_system->GetRValueReferenceType(m_type);
-  else
-    return CompilerType();
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetRValueReferenceType(m_type);
 }
 
 CompilerType CompilerType::GetAtomicType() const {
   if (IsValid())
-    return m_type_system->GetAtomicType(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetAtomicType(m_type);
   return CompilerType();
 }
 
 CompilerType CompilerType::AddConstModifier() const {
   if (IsValid())
-    return m_type_system->AddConstModifier(m_type);
-  else
-    return CompilerType();
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->AddConstModifier(m_type);
 }
 
 CompilerType CompilerType::AddVolatileModifier() const {
   if (IsValid())
-    return m_type_system->AddVolatileModifier(m_type);
-  else
-    return CompilerType();
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->AddVolatileModifier(m_type);
 }
 
 CompilerType CompilerType::AddRestrictModifier() const {
   if (IsValid())
-    return m_type_system->AddRestrictModifier(m_type);
-  else
-    return CompilerType();
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->AddRestrictModifier(m_type);
 }
 
 CompilerType CompilerType::CreateTypedef(const char *name,
                                          const CompilerDeclContext &decl_ctx,
                                          uint32_t payload) const {
   if (IsValid())
-    return m_type_system->CreateTypedef(m_type, name, decl_ctx, payload);
-  else
-    return CompilerType();
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->CreateTypedef(m_type, name, decl_ctx, payload);
 }
 
 CompilerType CompilerType::GetTypedefedType() const {
   if (IsValid())
-    return m_type_system->GetTypedefedType(m_type);
-  else
-    return CompilerType();
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetTypedefedType(m_type);
 }
 
 // Create related types using the current type's AST
 
 CompilerType
 CompilerType::GetBasicTypeFromAST(lldb::BasicType basic_type) const {
   if (IsValid())
-    return m_type_system->GetBasicTypeFromAST(basic_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetBasicTypeFromAST(basic_type);
   return CompilerType();
 }
 // Exploring the type
 
 llvm::Optional<uint64_t>
 CompilerType::GetBitSize(ExecutionContextScope *exe_scope) const {
   if (IsValid())
-    return m_type_system->GetBitSize(m_type, exe_scope);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetBitSize(m_type, exe_scope);
   return {};
 }
 
 llvm::Optional<uint64_t>
 CompilerType::GetByteSize(ExecutionContextScope *exe_scope) const {
   if (llvm::Optional<uint64_t> bit_size = GetBitSize(exe_scope))
     return (*bit_size + 7) / 8;
   return {};
 }
 
 llvm::Optional<size_t> CompilerType::GetTypeBitAlign(ExecutionContextScope *exe_scope) const {
   if (IsValid())
-    return m_type_system->GetTypeBitAlign(m_type, exe_scope);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetTypeBitAlign(m_type, exe_scope);
   return {};
 }
 
 lldb::Encoding CompilerType::GetEncoding(uint64_t &count) const {
-  if (!IsValid())
-    return lldb::eEncodingInvalid;
-
-  return m_type_system->GetEncoding(m_type, count);
+  if (IsValid())
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetEncoding(m_type, count);
 }
 
 lldb::Format CompilerType::GetFormat() const {
-  if (!IsValid())
-    return lldb::eFormatDefault;
-
-  return m_type_system->GetFormat(m_type);
+  if (IsValid())
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetFormat(m_type);
 }
 
 uint32_t CompilerType::GetNumChildren(bool omit_empty_base_classes,
                                       const ExecutionContext *exe_ctx) const {
-  if (!IsValid())
-    return 0;
-  return m_type_system->GetNumChildren(m_type, omit_empty_base_classes,
+  if (IsValid())
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetNumChildren(m_type, omit_empty_base_classes,
                                        exe_ctx);
+  return 0;
 }
 
 lldb::BasicType CompilerType::GetBasicTypeEnumeration() const {
   if (IsValid())
-    return m_type_system->GetBasicTypeEnumeration(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetBasicTypeEnumeration(m_type);
   return eBasicTypeInvalid;
 }
 
 void CompilerType::ForEachEnumerator(
     std::function<bool(const CompilerType &integer_type,
                        ConstString name,
                        const llvm::APSInt &value)> const &callback) const {
   if (IsValid())
-    return m_type_system->ForEachEnumerator(m_type, callback);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->ForEachEnumerator(m_type, callback);
 }
 
 uint32_t CompilerType::GetNumFields() const {
-  if (!IsValid())
-    return 0;
-  return m_type_system->GetNumFields(m_type);
+  if (IsValid())
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetNumFields(m_type);
 }
 
 CompilerType CompilerType::GetFieldAtIndex(size_t idx, std::string &name,
                                            uint64_t *bit_offset_ptr,
                                            uint32_t *bitfield_bit_size_ptr,
                                            bool *is_bitfield_ptr) const {
-  if (!IsValid())
-    return CompilerType();
-  return m_type_system->GetFieldAtIndex(m_type, idx, name, bit_offset_ptr,
+  if (IsValid())
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetFieldAtIndex(m_type, idx, name, bit_offset_ptr,
                                         bitfield_bit_size_ptr, is_bitfield_ptr);
+  return CompilerType();
 }
 
 uint32_t CompilerType::GetNumDirectBaseClasses() const {
   if (IsValid())
-    return m_type_system->GetNumDirectBaseClasses(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetNumDirectBaseClasses(m_type);
   return 0;
 }
 
 uint32_t CompilerType::GetNumVirtualBaseClasses() const {
   if (IsValid())
-    return m_type_system->GetNumVirtualBaseClasses(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetNumVirtualBaseClasses(m_type);
   return 0;
 }
 
 CompilerType
 CompilerType::GetDirectBaseClassAtIndex(size_t idx,
                                         uint32_t *bit_offset_ptr) const {
   if (IsValid())
-    return m_type_system->GetDirectBaseClassAtIndex(m_type, idx,
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetDirectBaseClassAtIndex(m_type, idx,
                                                     bit_offset_ptr);
   return CompilerType();
 }
 
 CompilerType
 CompilerType::GetVirtualBaseClassAtIndex(size_t idx,
                                          uint32_t *bit_offset_ptr) const {
   if (IsValid())
-    return m_type_system->GetVirtualBaseClassAtIndex(m_type, idx,
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetVirtualBaseClassAtIndex(m_type, idx,
                                                      bit_offset_ptr);
   return CompilerType();
 }
 
 uint32_t CompilerType::GetIndexOfFieldWithName(
     const char *name, CompilerType *field_compiler_type_ptr,
     uint64_t *bit_offset_ptr, uint32_t *bitfield_bit_size_ptr,
     bool *is_bitfield_ptr) const {

 CompilerType CompilerType::GetChildCompilerTypeAtIndex(
     ExecutionContext *exe_ctx, size_t idx, bool transparent_pointers,
     bool omit_empty_base_classes, bool ignore_array_bounds,
     std::string &child_name, uint32_t &child_byte_size,
     int32_t &child_byte_offset, uint32_t &child_bitfield_bit_size,
     uint32_t &child_bitfield_bit_offset, bool &child_is_base_class,
     bool &child_is_deref_of_parent, ValueObject *valobj,
     uint64_t &language_flags) const {
-  if (!IsValid())
-    return CompilerType();
-  return m_type_system->GetChildCompilerTypeAtIndex(
+  if (IsValid())
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetChildCompilerTypeAtIndex(
           m_type, exe_ctx, idx, transparent_pointers, omit_empty_base_classes,
           ignore_array_bounds, child_name, child_byte_size, child_byte_offset,
-      child_bitfield_bit_size, child_bitfield_bit_offset, child_is_base_class,
-      child_is_deref_of_parent, valobj, language_flags);
+          child_bitfield_bit_size, child_bitfield_bit_offset,
+          child_is_base_class, child_is_deref_of_parent, valobj,
+          language_flags);
+  return CompilerType();
 }
 
 // Look for a child member (doesn't include base classes, but it does include
 // their members) in the type hierarchy. Returns an index path into
 // "clang_type" on how to reach the appropriate member.
 //
 //    class A
 //    {

 // with: { 0,  1 } The first index 0 is the child index for "class A" within
 // class C (since class B doesn't have any members it doesn't count) The second
 // index 1 is the child index for "m_b" within class A
 
 size_t CompilerType::GetIndexOfChildMemberWithName(
     const char *name, bool omit_empty_base_classes,
     std::vector<uint32_t> &child_indexes) const {
   if (IsValid() && name && name[0]) {
-    return m_type_system->GetIndexOfChildMemberWithName(
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetIndexOfChildMemberWithName(
         m_type, name, omit_empty_base_classes, child_indexes);
   }
   return 0;
 }
 
 size_t CompilerType::GetNumTemplateArguments(bool expand_pack) const {
   if (IsValid()) {
-    return m_type_system->GetNumTemplateArguments(m_type, expand_pack);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetNumTemplateArguments(m_type, expand_pack);
   }
   return 0;
 }
 
 TemplateArgumentKind
 CompilerType::GetTemplateArgumentKind(size_t idx, bool expand_pack) const {
   if (IsValid())
-    return m_type_system->GetTemplateArgumentKind(m_type, idx, expand_pack);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetTemplateArgumentKind(m_type, idx, expand_pack);
   return eTemplateArgumentKindNull;
 }
 
 CompilerType CompilerType::GetTypeTemplateArgument(size_t idx,
                                                    bool expand_pack) const {
   if (IsValid()) {
-    return m_type_system->GetTypeTemplateArgument(m_type, idx, expand_pack);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetTypeTemplateArgument(m_type, idx, expand_pack);
   }
   return CompilerType();
 }
 
 llvm::Optional<CompilerType::IntegralTemplateArgument>
 CompilerType::GetIntegralTemplateArgument(size_t idx, bool expand_pack) const {
   if (IsValid())
-    return m_type_system->GetIntegralTemplateArgument(m_type, idx, expand_pack);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetIntegralTemplateArgument(m_type, idx, expand_pack);
   return llvm::None;
 }
 
 CompilerType CompilerType::GetTypeForFormatters() const {
   if (IsValid())
-    return m_type_system->GetTypeForFormatters(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetTypeForFormatters(m_type);
   return CompilerType();
 }
 
 LazyBool CompilerType::ShouldPrintAsOneLiner(ValueObject *valobj) const {
   if (IsValid())
-    return m_type_system->ShouldPrintAsOneLiner(m_type, valobj);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->ShouldPrintAsOneLiner(m_type, valobj);
   return eLazyBoolCalculate;
 }
 
 bool CompilerType::IsMeaninglessWithoutDynamicResolution() const {
   if (IsValid())
-    return m_type_system->IsMeaninglessWithoutDynamicResolution(m_type);
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->IsMeaninglessWithoutDynamicResolution(m_type);
   return false;
 }
 
 // Get the index of the child of "clang_type" whose name matches. This function
 // doesn't descend into the children, but only looks one level deep and name
 // matches can include base class names.
 
 uint32_t
 CompilerType::GetIndexOfChildWithName(const char *name,
                                       bool omit_empty_base_classes) const {
   if (IsValid() && name && name[0]) {
-    return m_type_system->GetIndexOfChildWithName(m_type, name,
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetIndexOfChildWithName(m_type, name,
                                                   omit_empty_base_classes);
   }
   return UINT32_MAX;
 }
 
 // Dumping types
 
 void CompilerType::DumpValue(ExecutionContext *exe_ctx, Stream *s,
                              lldb::Format format, const DataExtractor &data,
                              lldb::offset_t data_byte_offset,
                              size_t data_byte_size, uint32_t bitfield_bit_size,
                              uint32_t bitfield_bit_offset, bool show_types,
                              bool show_summary, bool verbose, uint32_t depth) {
   if (!IsValid())
-    return;
-  m_type_system->DumpValue(m_type, exe_ctx, s, format, data, data_byte_offset,
-                           data_byte_size, bitfield_bit_size,
-                           bitfield_bit_offset, show_types, show_summary,
-                           verbose, depth);
+    if (auto type_system_sp = GetTypeSystem())
+      type_system_sp->DumpValue(m_type, exe_ctx, s, format, data,
+                                data_byte_offset, data_byte_size,
+                                bitfield_bit_size, bitfield_bit_offset,
+                                show_types, show_summary, verbose, depth);
 }
 
 bool CompilerType::DumpTypeValue(Stream *s, lldb::Format format,
                                  const DataExtractor &data,
                                  lldb::offset_t byte_offset, size_t byte_size,
                                  uint32_t bitfield_bit_size,
                                  uint32_t bitfield_bit_offset,
                                  ExecutionContextScope *exe_scope) {
-  if (!IsValid())
-    return false;
-  return m_type_system->DumpTypeValue(m_type, s, format, data, byte_offset,
+  if (IsValid())
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->DumpTypeValue(m_type, s, format, data, byte_offset,
                                            byte_size, bitfield_bit_size,
                                            bitfield_bit_offset, exe_scope);
+  return false;
 }
 
 void CompilerType::DumpSummary(ExecutionContext *exe_ctx, Stream *s,
                                const DataExtractor &data,
                                lldb::offset_t data_byte_offset,
                                size_t data_byte_size) {
   if (IsValid())
-    m_type_system->DumpSummary(m_type, exe_ctx, s, data, data_byte_offset,
+    if (auto type_system_sp = GetTypeSystem())
+      type_system_sp->DumpSummary(m_type, exe_ctx, s, data, data_byte_offset,
                                   data_byte_size);
 }
 
 void CompilerType::DumpTypeDescription(lldb::DescriptionLevel level) const {
   if (IsValid())
-    m_type_system->DumpTypeDescription(m_type, level);
+    if (auto type_system_sp = GetTypeSystem())
+      type_system_sp->DumpTypeDescription(m_type, level);
 }
 
 void CompilerType::DumpTypeDescription(Stream *s,
                                        lldb::DescriptionLevel level) const {
-  if (IsValid()) {
-    m_type_system->DumpTypeDescription(m_type, s, level);
-  }
+  if (IsValid())
+    if (auto type_system_sp = GetTypeSystem())
+      type_system_sp->DumpTypeDescription(m_type, s, level);
 }
 
 #ifndef NDEBUG
 LLVM_DUMP_METHOD void CompilerType::dump() const {
   if (IsValid())
-    m_type_system->dump(m_type);
-  else
-    llvm::errs() << "<invalid>\n";
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->dump(m_type);
 }
 #endif
 
 bool CompilerType::GetValueAsScalar(const lldb_private::DataExtractor &data,
                                     lldb::offset_t data_byte_offset,
                                     size_t data_byte_size, Scalar &value,
                                     ExecutionContextScope *exe_scope) const {
   if (!IsValid())
case lldb::eEncodingIEEE754:
       break;
     }
   }
   return false;
 }
 
 #ifndef NDEBUG
 bool CompilerType::Verify() const {
-  return !IsValid() || m_type_system->Verify(m_type);
+  if (!IsValid())
+    return true;
+  if (auto type_system_sp = GetTypeSystem())
+    return type_system_sp->Verify(m_type);
+  return true;
 }
 #endif
 
+CompilerType::TypeSystemSPWrapper CompilerType::GetTypeSystem() const {
+  return {m_type_system.lock()};
+}
+
+bool CompilerType::TypeSystemSPWrapper::operator==(
+    const CompilerType::TypeSystemSPWrapper &other) const {
+  if (!m_typesystem_sp && !other.m_typesystem_sp)
+    return true;
+  if (m_typesystem_sp && other.m_typesystem_sp)
+    return m_typesystem_sp.get() == other.m_typesystem_sp.get();
+  return false;
+}
+
+TypeSystem *CompilerType::TypeSystemSPWrapper::operator->() const {
+  assert(m_typesystem_sp);
+  return m_typesystem_sp.get();
+}
+
 bool lldb_private::operator==(const lldb_private::CompilerType &lhs,
                               const lldb_private::CompilerType &rhs) {
   return lhs.GetTypeSystem() == rhs.GetTypeSystem() &&
          lhs.GetOpaqueQualType() == rhs.GetOpaqueQualType();
 }
 
 bool lldb_private::operator!=(const lldb_private::CompilerType &lhs,
                               const lldb_private::CompilerType &rhs) {
   return !(lhs == rhs);
 }

lldb/source/Symbol/SymbolFile.cpp

void SymbolFileCommon::SetCompileUnitAtIndex(uint32_t idx,
   // partial parsing should take care of only setting the compile unit
   // once, so if this assertion fails, we need to make sure that we don't
   // have a race condition, or have a second parse of the same compile
   // unit.
   assert((*m_compile_units)[idx] == nullptr);
   (*m_compile_units)[idx] = cu_sp;
 }
 
-llvm::Expected<TypeSystem &>
+llvm::Expected<TypeSystemSP>
 SymbolFileCommon::GetTypeSystemForLanguage(lldb::LanguageType language) {
   auto type_system_or_err =
       m_objfile_sp->GetModule()->GetTypeSystemForLanguage(language);
   if (type_system_or_err) {
-    type_system_or_err->SetSymbolFile(this);
+    if (auto ts = *type_system_or_err)
+      ts->SetSymbolFile(this);
   }
   return type_system_or_err;
 }
 
 uint64_t SymbolFileCommon::GetDebugInfoSize() {
   if (!m_objfile_sp)
     return 0;
   ModuleSP module_sp(m_objfile_sp->GetModule());

lldb/source/Symbol/SymbolFileOnDemand.cpp

void SymbolFileOnDemand::GetTypes(SymbolContextScope *sc_scope,
   if (!m_debug_info_enabled) {
     LLDB_LOG(GetLog(), "[{0}] {1} is skipped", GetSymbolFileName(),
              __FUNCTION__);
     return;
   }
   return m_sym_file_impl->GetTypes(sc_scope, type_mask, type_list);
 }
 
-llvm::Expected<TypeSystem &>
+llvm::Expected<lldb::TypeSystemSP>
 SymbolFileOnDemand::GetTypeSystemForLanguage(LanguageType language) {
   if (!m_debug_info_enabled) {
     Log *log = GetLog();
     LLDB_LOG(log, "[{0}] {1} is skipped for language type {2}",
              GetSymbolFileName(), __FUNCTION__, language);
     return llvm::make_error<llvm::StringError>(
         "GetTypeSystemForLanguage is skipped by SymbolFileOnDemand",
         llvm::inconvertibleErrorCode());

lldb/source/Symbol/Type.cpp

if (!m_compiler_type.IsValid()) {
     } else {
       // We have no encoding type, return void?
       auto type_system_or_err =
           m_symbol_file->GetTypeSystemForLanguage(eLanguageTypeC);
       if (auto err = type_system_or_err.takeError()) {
         LLDB_LOG_ERROR(GetLog(LLDBLog::Symbols), std::move(err),
                        "Unable to construct void type from TypeSystemClang");
       } else {
-        CompilerType void_compiler_type =
-            type_system_or_err->GetBasicTypeFromAST(eBasicTypeVoid);
+        CompilerType void_compiler_type;
+        auto ts = *type_system_or_err;
+        if (ts)
+          void_compiler_type = ts->GetBasicTypeFromAST(eBasicTypeVoid);
         switch (m_encoding_uid_type) {
         case eEncodingIsUID:
           m_compiler_type = void_compiler_type;
           break;
 
         case eEncodingIsConstUID:
           m_compiler_type = void_compiler_type.AddConstModifier();
           break;

 ModuleSP Type::GetModule() {
   if (m_symbol_file)
     return m_symbol_file->GetObjectFile()->GetModule();
   return ModuleSP();
 }
 
 ModuleSP Type::GetExeModule() {
   if (m_compiler_type) {
-    SymbolFile *symbol_file = m_compiler_type.GetTypeSystem()->GetSymbolFile();
+    auto ts = m_compiler_type.GetTypeSystem();
+    if (!ts)
+      return {};
+    SymbolFile *symbol_file = ts->GetSymbolFile();
     if (symbol_file)
       return symbol_file->GetObjectFile()->GetModule();
   }
-  return ModuleSP();
+  return {};
 }
 
 TypeAndOrName::TypeAndOrName(TypeSP &in_type_sp) {
   if (in_type_sp) {
     m_compiler_type = in_type_sp->GetForwardCompilerType();
     m_type_name = in_type_sp->GetName();
   }
 }
if (prefer_dynamic) {
       if (m_dynamic_type.IsValid())
         return m_dynamic_type;
     }
     return m_static_type;
   }
   return CompilerType();
 }
 
-TypeSystem *TypeImpl::GetTypeSystem(bool prefer_dynamic) {
+CompilerType::TypeSystemSPWrapper TypeImpl::GetTypeSystem(bool prefer_dynamic) {
   ModuleSP module_sp;
   if (CheckModule(module_sp)) {
     if (prefer_dynamic) {
       if (m_dynamic_type.IsValid())
         return m_dynamic_type.GetTypeSystem();
     }
     return m_static_type.GetTypeSystem();
   }
-  return nullptr;
+  return {};
 }
 
 bool TypeImpl::GetDescription(lldb_private::Stream &strm,
                               lldb::DescriptionLevel description_level) {
   ModuleSP module_sp;
   if (CheckModule(module_sp)) {
     if (m_dynamic_type.IsValid()) {
       strm.Printf("Dynamic:\n");

lldb/source/Symbol/TypeSystem.cpp

 //===-- TypeSystem.cpp ----------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "lldb/Symbol/TypeSystem.h"
 #include "lldb/Core/PluginManager.h"
 #include "lldb/Expression/UtilityFunction.h"
 #include "lldb/Symbol/CompilerType.h"
 #include "lldb/Target/Language.h"
 
-#include <set>
+#include "llvm/ADT/DenseSet.h"
 
 using namespace lldb_private;
 using namespace lldb;
 
 /// A 64-bit SmallBitVector is only small up to 64-7 bits, and the
 /// setBitsInMask interface wants to write full bytes.
 static const size_t g_num_small_bitvector_bits = 64 - 8;
 static_assert(eNumLanguageTypes < g_num_small_bitvector_bits,
               "Languages bit vector is no longer small on 64 bit systems");
 LanguageSet::LanguageSet() : bitvector(eNumLanguageTypes, false) {}
 
 llvm::Optional<LanguageType> LanguageSet::GetSingularLanguage() {
   if (bitvector.count() == 1)
     return (LanguageType)bitvector.find_first();
   return {};
 }
 
 void LanguageSet::Insert(LanguageType language) { bitvector.set(language); }
 size_t LanguageSet::Size() const { return bitvector.count(); }
 bool LanguageSet::Empty() const { return bitvector.none(); }
 bool LanguageSet::operator[](unsigned i) const { return bitvector[i]; }
 
 TypeSystem::~TypeSystem() = default;
 
-static lldb::TypeSystemSP CreateInstanceHelper(lldb::LanguageType language,
-                                               Module *module, Target *target) {
+static TypeSystemSP CreateInstanceHelper(lldb::LanguageType language,
   uint32_t i = 0;
   TypeSystemCreateInstance create_callback;
   while ((create_callback = PluginManager::GetTypeSystemCreateCallbackAtIndex(
               i++)) != nullptr) {
-    lldb::TypeSystemSP type_system_sp =
-        create_callback(language, module, target);
-    if (type_system_sp)
+    if (auto type_system_sp = create_callback(language, module, target))
       return type_system_sp;
   }
 
-  return lldb::TypeSystemSP();
+  return {};
 }
 
 lldb::TypeSystemSP TypeSystem::CreateInstance(lldb::LanguageType language,
                                               Module *module) {
   return CreateInstanceHelper(language, module, nullptr);
 }
 
 lldb::TypeSystemSP TypeSystem::CreateInstance(lldb::LanguageType language,
CompilerType TypeSystem::CreateTypedef(lldb::opaque_compiler_type_t type,
   return CompilerType();
 }
 
 CompilerType TypeSystem::GetBuiltinTypeByName(ConstString name) {
   return CompilerType();
 }
 
 CompilerType TypeSystem::GetTypeForFormatters(void *type) {
-  return CompilerType(this, type);
+  return CompilerType(weak_from_this(), type);
 }
 
 size_t TypeSystem::GetNumTemplateArguments(lldb::opaque_compiler_type_t type,
                                            bool expand_pack) {
   return 0;
 }
 
 TemplateArgumentKind

 
 void TypeSystemMap::Clear() {
   collection map;
   {
     std::lock_guard<std::mutex> guard(m_mutex);
     map = m_map;
     m_clear_in_progress = true;
   }
-  std::set<TypeSystem *> visited;
-  for (auto pair : map) {
-    TypeSystem *type_system = pair.second.get();
-    if (type_system && !visited.count(type_system)) {
-      visited.insert(type_system);
+  llvm::DenseSet<TypeSystem *> visited;
+  for (auto &pair : map) {
+    if (visited.count(pair.second.get()))
+      continue;
+    visited.insert(pair.second.get());
+    if (lldb::TypeSystemSP type_system = pair.second)
       type_system->Finalize();
-    }
-  }
   map.clear();
   {
     std::lock_guard<std::mutex> guard(m_mutex);
     m_map.clear();
     m_clear_in_progress = false;
   }
 }
 
-void TypeSystemMap::ForEach(std::function<bool(TypeSystem *)> const &callback) {
+void TypeSystemMap::ForEach(
+    std::function<bool(lldb::TypeSystemSP)> const &callback) {
   std::lock_guard<std::mutex> guard(m_mutex);
   // Use a std::set so we only call the callback once for each unique
-  // TypeSystem instance
-  std::set<TypeSystem *> visited;
-  for (auto pair : m_map) {
+  // TypeSystem instance.
+  llvm::DenseSet<TypeSystem *> visited;
+  for (auto &pair : m_map) {
     TypeSystem *type_system = pair.second.get();
-    if (type_system && !visited.count(type_system)) {
-      visited.insert(type_system);
-      if (!callback(type_system))
-        break;
-    }
-  }
-}
+    if (!type_system || visited.count(type_system))
+      continue;
+    assert(type_system);
+    if (!callback(pair.second))
 
-llvm::Expected<TypeSystem &> TypeSystemMap::GetTypeSystemForLanguage(
+llvm::Expected<lldb::TypeSystemSP> TypeSystemMap::GetTypeSystemForLanguage(
     lldb::LanguageType language,
     llvm::Optional<CreateCallback> create_callback) {
   std::lock_guard<std::mutex> guard(m_mutex);
   if (m_clear_in_progress)
     return llvm::make_error<llvm::StringError>(
         "Unable to get TypeSystem because TypeSystemMap is being cleared",
         llvm::inconvertibleErrorCode());
 
   collection::iterator pos = m_map.find(language);
   if (pos != m_map.end()) {
-    auto *type_system = pos->second.get();
-    if (type_system)
-      return *type_system;
+    if (pos->second) {
+      assert(!pos->second->weak_from_this().expired());
+      return pos->second;
+    }
     return llvm::make_error<llvm::StringError>(
         "TypeSystem for language " +
             llvm::StringRef(Language::GetNameForLanguageType(language)) +
             " doesn't exist",
         llvm::inconvertibleErrorCode());
   }
 
   for (const auto &pair : m_map) {
     if (pair.second && pair.second->SupportsLanguage(language)) {
       // Add a new mapping for "language" to point to an already existing
       // TypeSystem that supports this language
       m_map[language] = pair.second;
-      if (pair.second.get())
-        return *pair.second.get();
+      if (pair.second)
+        return pair.second;
       return llvm::make_error<llvm::StringError>(
           "TypeSystem for language " +
               llvm::StringRef(Language::GetNameForLanguageType(language)) +
               " doesn't exist",
           llvm::inconvertibleErrorCode());
     }
   }
 
   if (!create_callback)
     return llvm::make_error<llvm::StringError>(
         "Unable to find type system for language " +
             llvm::StringRef(Language::GetNameForLanguageType(language)),
         llvm::inconvertibleErrorCode());
 
   // Cache even if we get a shared pointer that contains a null type system
-  // back
+  // back.
   TypeSystemSP type_system_sp = (*create_callback)();
   m_map[language] = type_system_sp;
-  if (type_system_sp.get())
-    return *type_system_sp.get();
+  if (type_system_sp)
+    return type_system_sp;
   return llvm::make_error<llvm::StringError>(
       "TypeSystem for language " +
           llvm::StringRef(Language::GetNameForLanguageType(language)) +
           " doesn't exist",
       llvm::inconvertibleErrorCode());
 }
 
-llvm::Expected<TypeSystem &>
+llvm::Expected<lldb::TypeSystemSP>
 TypeSystemMap::GetTypeSystemForLanguage(lldb::LanguageType language,
                                         Module *module, bool can_create) {
   if (can_create) {
     return GetTypeSystemForLanguage(
         language, llvm::Optional<CreateCallback>([language, module]() {
           return TypeSystem::CreateInstance(language, module);
         }));
   }
   return GetTypeSystemForLanguage(language);
 }
 
-llvm::Expected<TypeSystem &>
+llvm::Expected<lldb::TypeSystemSP>
 TypeSystemMap::GetTypeSystemForLanguage(lldb::LanguageType language,
                                         Target *target, bool can_create) {
   if (can_create) {
     return GetTypeSystemForLanguage(
         language, llvm::Optional<CreateCallback>([language, target]() {
           return TypeSystem::CreateInstance(language, target);
         }));
   }
   return GetTypeSystemForLanguage(language);
 }

lldb/source/Target/Process.cpp

bool Process::CallVoidArgVoidPtrReturn(const Address *address,
   options.SetTrapExceptions(trap_exceptions);
 
   auto type_system_or_err =
       GetTarget().GetScratchTypeSystemForLanguage(eLanguageTypeC);
   if (!type_system_or_err) {
     llvm::consumeError(type_system_or_err.takeError());
     return false;
   }
+  auto ts = *type_system_or_err;
+  if (!ts)
+    return false;
   CompilerType void_ptr_type =
-      type_system_or_err->GetBasicTypeFromAST(eBasicTypeVoid).GetPointerType();
+      ts->GetBasicTypeFromAST(eBasicTypeVoid).GetPointerType();
   lldb::ThreadPlanSP call_plan_sp(new ThreadPlanCallFunction(
       *thread, *address, void_ptr_type, llvm::ArrayRef<addr_t>(), options));
   if (call_plan_sp) {
     DiagnosticManager diagnostics;
 
     StackFrame *frame = thread->GetStackFrameAtIndex(0).get();
     if (frame) {
       ExecutionContext exe_ctx;

lldb/source/Target/StackFrame.cpp

case Instruction::Operand::Type::Immediate: {
                                         addr)) {
         auto c_type_system_or_err =
             target_sp->GetScratchTypeSystemForLanguage(eLanguageTypeC);
         if (auto err = c_type_system_or_err.takeError()) {
           LLDB_LOG_ERROR(GetLog(LLDBLog::Thread), std::move(err),
                          "Unable to guess value for given address");
           return ValueObjectSP();
         } else {
+          auto ts = *c_type_system_or_err;
+          if (!ts)
+            return {};
           CompilerType void_ptr_type =
-              c_type_system_or_err
-                  ->GetBasicTypeFromAST(lldb::BasicType::eBasicTypeChar)
+              ts->GetBasicTypeFromAST(lldb::BasicType::eBasicTypeChar)
                   .GetPointerType();
           return ValueObjectMemory::Create(this, "", addr, void_ptr_type);
         }
       } else {
         return ValueObjectSP();
       }
       break;
     }

lldb/source/Target/Statistics.cpp

if (sym_file) {
       if (module_stat.debug_info_size > 0)
         ++num_modules_has_debug_info;
     }
     symtab_parse_time += module_stat.symtab_parse_time;
     symtab_index_time += module_stat.symtab_index_time;
     debug_parse_time += module_stat.debug_parse_time;
     debug_index_time += module_stat.debug_index_time;
     debug_info_size += module_stat.debug_info_size;
-    module->ForEachTypeSystem([&](TypeSystem *ts) {
+    module->ForEachTypeSystem([&](lldb::TypeSystemSP ts) {
       if (auto stats = ts->ReportStatistics())
         module_stat.type_system_stats.insert({ts->GetPluginName(), *stats});
       return true;
     });
     json_modules.emplace_back(module_stat.ToJSON());
   }
 
   ConstStringStats const_string_stats;

lldb/source/Target/Target.cpp

 void Target::ImageSearchPathsChanged(const PathMappingList &path_list,
                                      void *baton) {
   Target *target = (Target *)baton;
   ModuleSP exe_module_sp(target->GetExecutableModule());
   if (exe_module_sp)
     target->SetExecutableModule(exe_module_sp, eLoadDependentsYes);
 }
 
-llvm::Expected<TypeSystem &>
+llvm::Expected<lldb::TypeSystemSP>
 Target::GetScratchTypeSystemForLanguage(lldb::LanguageType language,
                                         bool create_on_demand) {
   if (!m_valid)
     return llvm::make_error<llvm::StringError>("Invalid Target",
                                                llvm::inconvertibleErrorCode());
 
   if (language == eLanguageTypeMipsAssembler // GNU AS and LLVM use it for all
                                              // assembly code
if (languages_for_expressions[eLanguageTypeC]) {
       language = (LanguageType)languages_for_expressions.bitvector.find_first();
     }
   }
 
   return m_scratch_type_system_map.GetTypeSystemForLanguage(language, this,
                                                             create_on_demand);
 }
 
-std::vector<TypeSystem *> Target::GetScratchTypeSystems(bool create_on_demand) {
+std::vector<lldb::TypeSystemSP>
+Target::GetScratchTypeSystems(bool create_on_demand) {
   if (!m_valid)
     return {};
 
   // Some TypeSystem instances are associated with several LanguageTypes so
   // they will show up several times in the loop below. The SetVector filters
   // out all duplicates as they serve no use for the caller.
-  llvm::SetVector<TypeSystem *> scratch_type_systems;
+  std::vector<lldb::TypeSystemSP> scratch_type_systems;
 
   LanguageSet languages_for_expressions =
       Language::GetLanguagesSupportingTypeSystemsForExpressions();
 
   for (auto bit : languages_for_expressions.bitvector.set_bits()) {
     auto language = (LanguageType)bit;
     auto type_system_or_err =
         GetScratchTypeSystemForLanguage(language, create_on_demand);
     if (!type_system_or_err)
       LLDB_LOG_ERROR(GetLog(LLDBLog::Target), type_system_or_err.takeError(),
                      "Language '{}' has expression support but no scratch type "
                      "system available",
                      Language::GetNameForLanguageType(language));
     else
-      scratch_type_systems.insert(&type_system_or_err.get());
+      if (auto ts = *type_system_or_err)
+        scratch_type_systems.push_back(ts);
   }
-
-  return scratch_type_systems.takeVector();
+  std::sort(scratch_type_systems.begin(), scratch_type_systems.end(),
+            [](lldb::TypeSystemSP a, lldb::TypeSystemSP b) {
+              return a.get() <= b.get();
+            });
+  scratch_type_systems.erase(
+      std::unique(scratch_type_systems.begin(), scratch_type_systems.end()));
+  return scratch_type_systems;
 }
 
 PersistentExpressionState *
 Target::GetPersistentExpressionStateForLanguage(lldb::LanguageType language) {
   auto type_system_or_err = GetScratchTypeSystemForLanguage(language, true);
 
   if (auto err = type_system_or_err.takeError()) {
     LLDB_LOG_ERROR(GetLog(LLDBLog::Target), std::move(err),
                    "Unable to get persistent expression state for language {}",
                    Language::GetNameForLanguageType(language));
     return nullptr;
   }
 
-  return type_system_or_err->GetPersistentExpressionState();
+  if (auto ts = *type_system_or_err)
+    return ts->GetPersistentExpressionState();
+
+  LLDB_LOG(GetLog(LLDBLog::Target),
+           "Unable to get persistent expression state for language {}",
+           Language::GetNameForLanguageType(language));
+  return nullptr;
 }
 
 UserExpression *Target::GetUserExpressionForLanguage(
     llvm::StringRef expr, llvm::StringRef prefix, lldb::LanguageType language,
     Expression::ResultType desired_type,
     const EvaluateExpressionOptions &options, ValueObject *ctx_obj,
     Status &error) {
   auto type_system_or_err = GetScratchTypeSystemForLanguage(language);
   if (auto err = type_system_or_err.takeError()) {
     error.SetErrorStringWithFormat(
         "Could not find type system for language %s: %s",
         Language::GetNameForLanguageType(language),
         llvm::toString(std::move(err)).c_str());
     return nullptr;
   }
 
-  auto *user_expr = type_system_or_err->GetUserExpression(
-      expr, prefix, language, desired_type, options, ctx_obj);
+  auto ts = *type_system_or_err;
+  if (!ts) {
+    error.SetErrorStringWithFormat(
+        "Type system for language %s is no longer live",
+        Language::GetNameForLanguageType(language));
+    return nullptr;
+  }
+
+  auto *user_expr = ts->GetUserExpression(expr, prefix, language, desired_type,
+                                          options, ctx_obj);
   if (!user_expr)
     error.SetErrorStringWithFormat(
         "Could not create an expression for language %s",
         Language::GetNameForLanguageType(language));
 
   return user_expr;
 }
 
 FunctionCaller *Target::GetFunctionCallerForLanguage(
     lldb::LanguageType language, const CompilerType &return_type,
     const Address &function_address, const ValueList &arg_value_list,
     const char *name, Status &error) {
   auto type_system_or_err = GetScratchTypeSystemForLanguage(language);
   if (auto err = type_system_or_err.takeError()) {
     error.SetErrorStringWithFormat(
         "Could not find type system for language %s: %s",
         Language::GetNameForLanguageType(language),
         llvm::toString(std::move(err)).c_str());
     return nullptr;
   }
-
-  auto *persistent_fn = type_system_or_err->GetFunctionCaller(
-      return_type, function_address, arg_value_list, name);
+  auto ts = *type_system_or_err;
+  if (!ts) {
+    error.SetErrorStringWithFormat(
+        "Type system for language %s is no longer live",
+        Language::GetNameForLanguageType(language));
+    return nullptr;
+  }
+  auto *persistent_fn = ts->GetFunctionCaller(return_type, function_address,
+                                              arg_value_list, name);
   if (!persistent_fn)
     error.SetErrorStringWithFormat(
         "Could not create an expression for language %s",
         Language::GetNameForLanguageType(language));
 
   return persistent_fn;
 }
 
 llvm::Expected<std::unique_ptr<UtilityFunction>>
 Target::CreateUtilityFunction(std::string expression, std::string name,
                               lldb::LanguageType language,
                               ExecutionContext &exe_ctx) {
   auto type_system_or_err = GetScratchTypeSystemForLanguage(language);
   if (!type_system_or_err)
     return type_system_or_err.takeError();
-
+  auto ts = *type_system_or_err;
+  if (!ts)
+    return llvm::make_error<llvm::StringError>(
+        llvm::StringRef("Type system for language ") +
+            Language::GetNameForLanguageType(language) +
+            llvm::StringRef(" is no longer live"),
+        llvm::inconvertibleErrorCode());
   std::unique_ptr<UtilityFunction> utility_fn =
-      type_system_or_err->CreateUtilityFunction(std::move(expression),
-                                                std::move(name));
+      ts->CreateUtilityFunction(std::move(expression), std::move(name));
   if (!utility_fn)
     return llvm::make_error<llvm::StringError>(
         llvm::StringRef("Could not create an expression for language") +
             Language::GetNameForLanguageType(language),
         llvm::inconvertibleErrorCode());
 
   DiagnosticManager diagnostics;
   if (!utility_fn->Install(diagnostics, exe_ctx))
ExpressionResults Target::EvaluateExpression(
   lldb::ExpressionVariableSP persistent_var_sp;
   if (expr[0] == '$') {
     auto type_system_or_err =
             GetScratchTypeSystemForLanguage(eLanguageTypeC);
     if (auto err = type_system_or_err.takeError()) {
       LLDB_LOG_ERROR(GetLog(LLDBLog::Target), std::move(err),
                      "Unable to get scratch type system");
     } else {
+      auto ts = *type_system_or_err;
+      if (!ts)
+        LLDB_LOG_ERROR(GetLog(LLDBLog::Target), std::move(err),
+                       "Scratch type system is no longer live");
+      else
         persistent_var_sp =
-          type_system_or_err->GetPersistentExpressionState()->GetVariable(expr);
+            ts->GetPersistentExpressionState()->GetVariable(expr);
     }
   }
   if (persistent_var_sp) {
     result_valobj_sp = persistent_var_sp->GetValueObject();
     execution_results = eExpressionCompleted;
   } else {
     llvm::StringRef prefix = GetExpressionPrefixContents();
     Status error;
ExpressionResults Target::EvaluateExpression(
   else
     m_stats.GetExpressionStats().NotifyFailure();
   return execution_results;
 }
 
 lldb::ExpressionVariableSP Target::GetPersistentVariable(ConstString name) {
   lldb::ExpressionVariableSP variable_sp;
   m_scratch_type_system_map.ForEach(
-      [name, &variable_sp](TypeSystem *type_system) -> bool {
+      [name, &variable_sp](TypeSystemSP type_system) -> bool {
+        auto ts = type_system.get();
+        if (!ts)
+          return true;
         if (PersistentExpressionState *persistent_state =
-                type_system->GetPersistentExpressionState()) {
+                ts->GetPersistentExpressionState()) {
           variable_sp = persistent_state->GetVariable(name);
 
           if (variable_sp)
             return false; // Stop iterating the ForEach
         }
         return true; // Keep iterating the ForEach
       });
   return variable_sp;
 }
 
 lldb::addr_t Target::GetPersistentSymbol(ConstString name) {
   lldb::addr_t address = LLDB_INVALID_ADDRESS;
 
   m_scratch_type_system_map.ForEach(
-      [name, &address](TypeSystem *type_system) -> bool {
+      [name, &address](lldb::TypeSystemSP type_system) -> bool {
+        auto ts = type_system.get();
+        if (!ts)
+          return true;
+
         if (PersistentExpressionState *persistent_state =
-                type_system->GetPersistentExpressionState()) {
+                ts->GetPersistentExpressionState()) {
           address = persistent_state->LookupSymbol(name);
           if (address != LLDB_INVALID_ADDRESS)
             return false; // Stop iterating the ForEach
         }
         return true; // Keep iterating the ForEach
       });
   return address;
 }

lldb/source/Target/ThreadPlanTracer.cpp

TypeFromUser ThreadPlanAssemblyTracer::GetIntPointerType() {
   if (!m_intptr_type.IsValid()) {
     if (auto target_sp = m_process.CalculateTarget()) {
       auto type_system_or_err =
           target_sp->GetScratchTypeSystemForLanguage(eLanguageTypeC);
       if (auto err = type_system_or_err.takeError()) {
         LLDB_LOG_ERROR(GetLog(LLDBLog::Types), std::move(err),
                        "Unable to get integer pointer type from TypeSystem");
       } else {
-        m_intptr_type = TypeFromUser(
-            type_system_or_err->GetBuiltinTypeForEncodingAndBitSize(
-                eEncodingUint,
-                target_sp->GetArchitecture().GetAddressByteSize() * 8));
+        if (auto ts = *type_system_or_err)
+          m_intptr_type = TypeFromUser(ts->GetBuiltinTypeForEncodingAndBitSize(
       }
     }
   }
   return m_intptr_type;
 }
 
 ThreadPlanAssemblyTracer::~ThreadPlanAssemblyTracer() = default;
 

lldb/tools/lldb-test/lldb-test.cpp

 
 Error opts::symbols::dumpAST(lldb_private::Module &Module) {
   Module.ParseAllDebugSymbols();
 
   SymbolFile *symfile = Module.GetSymbolFile();
   if (!symfile)
     return make_string_error("Module has no symbol file.");
 
-  llvm::Expected<TypeSystem &> type_system_or_err =
+  auto type_system_or_err =
       symfile->GetTypeSystemForLanguage(eLanguageTypeC_plus_plus);
   if (!type_system_or_err)
     return make_string_error("Can't retrieve TypeSystemClang");
 
-  auto *clang_ast_ctx =
-      llvm::dyn_cast_or_null<TypeSystemClang>(&type_system_or_err.get());
+  auto ts = *type_system_or_err;
+  auto *clang_ast_ctx = llvm::dyn_cast_or_null<TypeSystemClang>(ts.get());
   if (!clang_ast_ctx)
     return make_string_error("Retrieved TypeSystem was not a TypeSystemClang");
 
   clang::ASTContext &ast_ctx = clang_ast_ctx->getASTContext();
 
   clang::TranslationUnitDecl *tu = ast_ctx.getTranslationUnitDecl();
   if (!tu)
     return make_string_error("Can't retrieve translation unit declaration.");
 
   tu->print(outs());
 
   return Error::success();
 }
 
 Error opts::symbols::dumpEntireClangAST(lldb_private::Module &Module) {
   Module.ParseAllDebugSymbols();
 
   SymbolFile *symfile = Module.GetSymbolFile();
   if (!symfile)
     return make_string_error("Module has no symbol file.");
 
-  llvm::Expected<TypeSystem &> type_system_or_err =
+  auto type_system_or_err =
       symfile->GetTypeSystemForLanguage(eLanguageTypeObjC_plus_plus);
   if (!type_system_or_err)
     return make_string_error("Can't retrieve TypeSystemClang");
-
-  auto *clang_ast_ctx =
-      llvm::dyn_cast_or_null<TypeSystemClang>(&type_system_or_err.get());
+  auto ts = *type_system_or_err;
+  auto *clang_ast_ctx = llvm::dyn_cast_or_null<TypeSystemClang>(ts.get());
   if (!clang_ast_ctx)
     return make_string_error("Retrieved TypeSystem was not a TypeSystemClang");
 
   StreamString Stream;
   clang_ast_ctx->DumpFromSymbolFile(Stream, Name);
   outs() << Stream.GetData() << "\n";
 
   return Error::success();

lldb/unittests/Expression/ClangExpressionDeclMapTest.cpp

 using namespace lldb_private;
 using namespace lldb;
 
 namespace {
 struct FakeClangExpressionDeclMap : public ClangExpressionDeclMap {
   FakeClangExpressionDeclMap(const std::shared_ptr<ClangASTImporter> &importer)
       : ClangExpressionDeclMap(false, nullptr, lldb::TargetSP(), importer,
                                nullptr) {
-    m_scratch_context = clang_utils::createAST();
+    m_holder = std::make_unique<clang_utils::TypeSystemClangHolder>("ast");
+    m_scratch_context = m_holder->GetAST();
   }
-  std::unique_ptr<TypeSystemClang> m_scratch_context;
+  std::unique_ptr<clang_utils::TypeSystemClangHolder> m_holder;
+  TypeSystemClang *m_scratch_context;
   /// Adds a persistent decl that can be found by the ClangExpressionDeclMap
   /// via GetPersistentDecl.
   void AddPersistentDeclForTest(clang::NamedDecl *d) {
     // The declaration needs to have '$' prefix in its name like every
     // persistent declaration and must be inside the scratch AST context.
     assert(d);
     assert(d->getName().startswith("$"));
     assert(&d->getASTContext() == &m_scratch_context->getASTContext());

 struct ClangExpressionDeclMapTest : public testing::Test {
   SubsystemRAII<FileSystem, HostInfo> subsystems;
 
   /// The ClangASTImporter used during the test.
   std::shared_ptr<ClangASTImporter> importer;
   /// The ExpressionDeclMap for the current test case.
   std::unique_ptr<FakeClangExpressionDeclMap> decl_map;
 
+  std::unique_ptr<clang_utils::TypeSystemClangHolder> holder;
+  
   /// The target AST that lookup results should be imported to.
-  std::unique_ptr<TypeSystemClang> target_ast;
+  TypeSystemClang *target_ast;
 
   void SetUp() override {
     importer = std::make_shared<ClangASTImporter>();
     decl_map = std::make_unique<FakeClangExpressionDeclMap>(importer);
-    target_ast = clang_utils::createAST();
+    holder = std::make_unique<clang_utils::TypeSystemClangHolder>("target ast");
+    target_ast = holder->GetAST();
     decl_map->InstallASTContext(*target_ast);
   }
 
   void TearDown() override {
     importer.reset();
     decl_map.reset();
-    target_ast.reset();
+    holder.reset();
   }
 };
 } // namespace
 
 TEST_F(ClangExpressionDeclMapTest, TestUnknownIdentifierLookup) {
   // Tests looking up an identifier that can't be found anywhere.
 
   // Setup a NameSearchContext for 'foo'.

lldb/unittests/Symbol/TestClangASTImporter.cpp

TEST_F(TestClangASTImporter, ImportInvalidType) {
   ClangASTImporter importer;
   EXPECT_FALSE(importer.Import(CompilerType()));
 }
 
 TEST_F(TestClangASTImporter, CopyDeclTagDecl) {
   // Tests that the ClangASTImporter::CopyDecl can copy TagDecls.
   clang_utils::SourceASTWithRecord source;
 
-  std::unique_ptr<TypeSystemClang> target_ast = clang_utils::createAST();
+  auto holder =
+      std::make_unique<clang_utils::TypeSystemClangHolder>("target ast");
+  auto *target_ast = holder->GetAST();
 
   ClangASTImporter importer;
   clang::Decl *imported =
       importer.CopyDecl(&target_ast->getASTContext(), source.record_decl);
   ASSERT_NE(nullptr, imported);
 
   // Check that we got the correct decl by just comparing their qualified name.
   clang::TagDecl *imported_tag_decl = llvm::cast<clang::TagDecl>(imported);
   EXPECT_EQ(source.record_decl->getQualifiedNameAsString(),
             imported_tag_decl->getQualifiedNameAsString());
   // We did a minimal import of the tag decl.
   EXPECT_TRUE(imported_tag_decl->hasExternalLexicalStorage());
 
   // Check that origin was set for the imported declaration.
   ClangASTImporter::DeclOrigin origin = importer.GetDeclOrigin(imported);
   EXPECT_TRUE(origin.Valid());
   EXPECT_EQ(origin.ctx, &source.ast->getASTContext());
   EXPECT_EQ(origin.decl, source.record_decl);
 }
 
 TEST_F(TestClangASTImporter, CopyTypeTagDecl) {
   // Tests that the ClangASTImporter::CopyType can copy TagDecls types.
   clang_utils::SourceASTWithRecord source;
 
-  std::unique_ptr<TypeSystemClang> target_ast = clang_utils::createAST();
+  auto holder =
+      std::make_unique<clang_utils::TypeSystemClangHolder>("target ast");
+  auto *target_ast = holder->GetAST();
 
   ClangASTImporter importer;
   CompilerType imported = importer.CopyType(*target_ast, source.record_type);
   ASSERT_TRUE(imported.IsValid());
 
   // Check that we got the correct decl by just comparing their qualified name.
   clang::TagDecl *imported_tag_decl = ClangUtil::GetAsTagDecl(imported);
   EXPECT_EQ(source.record_decl->getQualifiedNameAsString(),

 }
 
 TEST_F(TestClangASTImporter, CompleteFwdDeclWithOtherOrigin) {
   // Create an AST with a full type that is defined.
   clang_utils::SourceASTWithRecord source_with_definition;
 
   // Create an AST with a type thst is only a forward declaration with the
   // same name as the one in the other source.
-  std::unique_ptr<TypeSystemClang> fwd_decl_source = clang_utils::createAST();
+  auto holder =
+      std::make_unique<clang_utils::TypeSystemClangHolder>("ast");
+  auto *fwd_decl_source = holder->GetAST();
   CompilerType fwd_decl_type = clang_utils::createRecord(
       *fwd_decl_source, source_with_definition.record_decl->getName());
 
   // Create a target and import the forward decl.
-  std::unique_ptr<TypeSystemClang> target = clang_utils::createAST();
+  auto target_holder =
+      std::make_unique<clang_utils::TypeSystemClangHolder>("target ast");
+  auto *target = target_holder->GetAST();
   ClangASTImporter importer;
   CompilerType imported = importer.CopyType(*target, fwd_decl_type);
   ASSERT_TRUE(imported.IsValid());
   EXPECT_FALSE(imported.IsDefined());
 
   // Now complete the forward decl with the definition from the other source.
   // This should define the decl and give it the fields of the other origin.
   clang::TagDecl *imported_tag_decl = ClangUtil::GetAsTagDecl(imported);
   importer.CompleteTagDeclWithOrigin(imported_tag_decl,
                                      source_with_definition.record_decl);
   ASSERT_TRUE(imported.IsValid());
   EXPECT_TRUE(imported.IsDefined());
   EXPECT_EQ(1U, imported.GetNumFields());
 }
 
 TEST_F(TestClangASTImporter, DeportDeclTagDecl) {
   // Tests that the ClangASTImporter::DeportDecl completely copies TagDecls.
   clang_utils::SourceASTWithRecord source;
 
-  std::unique_ptr<TypeSystemClang> target_ast = clang_utils::createAST();
+  auto holder =
+      std::make_unique<clang_utils::TypeSystemClangHolder>("target ast");
+  auto *target_ast = holder->GetAST();
 
   ClangASTImporter importer;
   clang::Decl *imported =
       importer.DeportDecl(&target_ast->getASTContext(), source.record_decl);
   ASSERT_NE(nullptr, imported);
 
   // Check that we got the correct decl by just comparing their qualified name.
   clang::TagDecl *imported_tag_decl = llvm::cast<clang::TagDecl>(imported);
   EXPECT_EQ(source.record_decl->getQualifiedNameAsString(),
             imported_tag_decl->getQualifiedNameAsString());
   // The record should be completed as we deported it.
   EXPECT_FALSE(imported_tag_decl->hasExternalLexicalStorage());
 
   // Deporting doesn't update the origin map.
   EXPECT_FALSE(importer.GetDeclOrigin(imported_tag_decl).Valid());
 }
 
 TEST_F(TestClangASTImporter, DeportTypeTagDecl) {
   // Tests that the ClangASTImporter::CopyType can deport TagDecl types.
   clang_utils::SourceASTWithRecord source;
 
-  std::unique_ptr<TypeSystemClang> target_ast = clang_utils::createAST();
+  auto holder =
+      std::make_unique<clang_utils::TypeSystemClangHolder>("target ast");
+  auto *target_ast = holder->GetAST();
 
   ClangASTImporter importer;
   CompilerType imported = importer.DeportType(*target_ast, source.record_type);
   ASSERT_TRUE(imported.IsValid());
 
   // Check that we got the correct decl by just comparing their qualified name.
   clang::TagDecl *imported_tag_decl = ClangUtil::GetAsTagDecl(imported);
   EXPECT_EQ(source.record_decl->getQualifiedNameAsString(),
             imported_tag_decl->getQualifiedNameAsString());
   // The record should be completed as we deported it.
   EXPECT_FALSE(imported_tag_decl->hasExternalLexicalStorage());
 
   // Deporting doesn't update the origin map.
   EXPECT_FALSE(importer.GetDeclOrigin(imported_tag_decl).Valid());
 }
 
 TEST_F(TestClangASTImporter, MetadataPropagation) {
   // Tests that AST metadata is propagated when copying declarations.
 
   clang_utils::SourceASTWithRecord source;
 
   const lldb::user_id_t metadata = 123456;
   source.ast->SetMetadataAsUserID(source.record_decl, metadata);
 
-  std::unique_ptr<TypeSystemClang> target_ast = clang_utils::createAST();
+  auto holder =
+      std::make_unique<clang_utils::TypeSystemClangHolder>("target ast");
+  auto *target_ast = holder->GetAST();
 
   ClangASTImporter importer;
   clang::Decl *imported =
       importer.CopyDecl(&target_ast->getASTContext(), source.record_decl);
   ASSERT_NE(nullptr, imported);
 
   // Check that we got the same Metadata.
   ASSERT_NE(nullptr, importer.GetDeclMetadata(imported));
   EXPECT_EQ(metadata, importer.GetDeclMetadata(imported)->GetUserID());
 }
 
 TEST_F(TestClangASTImporter, MetadataPropagationIndirectImport) {
   // Tests that AST metadata is propagated when copying declarations when
   // importing one declaration into a temporary context and then to the
   // actual destination context.
 
   clang_utils::SourceASTWithRecord source;
 
   const lldb::user_id_t metadata = 123456;
   source.ast->SetMetadataAsUserID(source.record_decl, metadata);
 
-  std::unique_ptr<TypeSystemClang> temporary_ast = clang_utils::createAST();
+  auto tmp_holder =
+      std::make_unique<clang_utils::TypeSystemClangHolder>("tmp ast");
+  auto *temporary_ast = tmp_holder->GetAST();
 
   ClangASTImporter importer;
   clang::Decl *temporary_imported =
       importer.CopyDecl(&temporary_ast->getASTContext(), source.record_decl);
   ASSERT_NE(nullptr, temporary_imported);
 
-  std::unique_ptr<TypeSystemClang> target_ast = clang_utils::createAST();
+  auto holder =
+      std::make_unique<clang_utils::TypeSystemClangHolder>("target ast");
+  auto *target_ast = holder->GetAST();
   clang::Decl *imported =
       importer.CopyDecl(&target_ast->getASTContext(), temporary_imported);
   ASSERT_NE(nullptr, imported);
 
   // Check that we got the same Metadata.
   ASSERT_NE(nullptr, importer.GetDeclMetadata(imported));
   EXPECT_EQ(metadata, importer.GetDeclMetadata(imported)->GetUserID());
 }
 
 TEST_F(TestClangASTImporter, MetadataPropagationAfterCopying) {
   // Tests that AST metadata is propagated when copying declarations even
   // when the metadata was set after the declaration has already been copied.
 
   clang_utils::SourceASTWithRecord source;
   const lldb::user_id_t metadata = 123456;
 
-  std::unique_ptr<TypeSystemClang> target_ast = clang_utils::createAST();
+  auto holder =
+      std::make_unique<clang_utils::TypeSystemClangHolder>("target ast");
+  auto *target_ast = holder->GetAST();
 
   ClangASTImporter importer;
   clang::Decl *imported =
       importer.CopyDecl(&target_ast->getASTContext(), source.record_decl);
   ASSERT_NE(nullptr, imported);
 
   // The TagDecl has been imported. Now set the metadata of the source and
   // make sure the imported one will directly see it.

lldb/unittests/Symbol/TestTypeSystemClang.cpp

 using namespace lldb;
 using namespace lldb_private;
 
 class TestTypeSystemClang : public testing::Test {
 public:
   SubsystemRAII<FileSystem, HostInfo> subsystems;
 
   void SetUp() override {
-    m_ast.reset(
-        new TypeSystemClang("test ASTContext", HostInfo::GetTargetTriple()));
+    m_holder =
+        std::make_unique<clang_utils::TypeSystemClangHolder>("test ASTContext");
+    m_ast = m_holder->GetAST();
   }
 
-  void TearDown() override { m_ast.reset(); }
+  void TearDown() override {
+    m_ast = nullptr;
+    m_holder.reset();
+  }
 
 protected:
-  std::unique_ptr<TypeSystemClang> m_ast;
+  
+  TypeSystemClang *m_ast = nullptr;
+  std::unique_ptr<clang_utils::TypeSystemClangHolder> m_holder;
 
   QualType GetBasicQualType(BasicType type) const {
     return ClangUtil::GetQualType(m_ast->GetBasicTypeFromAST(type));
   }
 
   QualType GetBasicQualType(const char *name) const {
     return ClangUtil::GetQualType(
         m_ast->GetBuiltinTypeByName(ConstString(name)));
const std::vector<lldb::BasicType> types_to_test = {
       eBasicTypeUnsignedLong, eBasicTypeLongLong,    eBasicTypeUnsignedLongLong,
   };
 
   for (bool scoped : {true, false}) {
     SCOPED_TRACE("scoped: " + std::to_string(scoped));
     for (lldb::BasicType basic_type : types_to_test) {
       SCOPED_TRACE(std::to_string(basic_type));
 
-      TypeSystemClang ast("enum_ast", HostInfo::GetTargetTriple());
+      auto holder =
+          std::make_unique<clang_utils::TypeSystemClangHolder>("enum_ast");
+      auto &ast = *holder->GetAST();
+
       CompilerType basic_compiler_type = ast.GetBasicType(basic_type);
       EXPECT_TRUE(basic_compiler_type.IsValid());
 
       CompilerType enum_type = ast.CreateEnumerationType(
           "my_enum", ast.GetTranslationUnitDecl(), OptionalClangModuleID(),
           Declaration(), basic_compiler_type, scoped);
 
       CompilerType t = ast.GetEnumerationIntegerType(enum_type);
       // Check that the type we put in at the start is found again.
       EXPECT_EQ(basic_compiler_type.GetTypeName(), t.GetTypeName());
     }
   }
 }
 
 TEST_F(TestTypeSystemClang, TestOwningModule) {
-  TypeSystemClang ast("module_ast", HostInfo::GetTargetTriple());
+  auto holder =
+      std::make_unique<clang_utils::TypeSystemClangHolder>("module_ast");
+  auto &ast = *holder->GetAST();
   CompilerType basic_compiler_type = ast.GetBasicType(BasicType::eBasicTypeInt);
   CompilerType enum_type = ast.CreateEnumerationType(
       "my_enum", ast.GetTranslationUnitDecl(), OptionalClangModuleID(100),
       Declaration(), basic_compiler_type, false);
   auto *ed = TypeSystemClang::GetAsEnumDecl(enum_type);
   EXPECT_FALSE(!ed);
   EXPECT_EQ(ed->getOwningModuleID(), 100u);
 
TEST_F(TestTypeSystemClang, TestOwningModule) {
   EXPECT_FALSE(!cd);
   EXPECT_EQ(cd->getOwningModuleID(), 300u);
 }
 
 TEST_F(TestTypeSystemClang, TestIsClangType) {
   clang::ASTContext &context = m_ast->getASTContext();
   lldb::opaque_compiler_type_t bool_ctype =
       TypeSystemClang::GetOpaqueCompilerType(&context, lldb::eBasicTypeBool);
-  CompilerType bool_type(m_ast.get(), bool_ctype);
+  CompilerType bool_type(m_ast->weak_from_this(), bool_ctype);
   CompilerType record_type = m_ast->CreateRecordType(
       nullptr, OptionalClangModuleID(100), lldb::eAccessPublic, "FooRecord",
       clang::TTK_Struct, lldb::eLanguageTypeC_plus_plus, nullptr);
   // Clang builtin type and record type should pass
   EXPECT_TRUE(ClangUtil::IsClangType(bool_type));
   EXPECT_TRUE(ClangUtil::IsClangType(record_type));
 
   // Default constructed type should fail
TEST_F(TestTypeSystemClang, TemplateArguments) {
   m_ast->StartTagDeclarationDefinition(type);
   m_ast->CompleteTagDeclarationDefinition(type);
 
   // typedef foo<int, 47> foo_def;
   CompilerType typedef_type = type.CreateTypedef(
       "foo_def", m_ast->CreateDeclContext(m_ast->GetTranslationUnitDecl()), 0);
 
   CompilerType auto_type(
-      m_ast.get(),
+      m_ast->weak_from_this(),
       m_ast->getASTContext()
           .getAutoType(ClangUtil::GetCanonicalQualType(typedef_type),
                        clang::AutoTypeKeyword::Auto, false)
           .getAsOpaquePtr());
 
-  CompilerType int_type(m_ast.get(),
+  CompilerType int_type(m_ast->weak_from_this(),
                         m_ast->getASTContext().IntTy.getAsOpaquePtr());
   for (CompilerType t : {type, typedef_type, auto_type}) {
     SCOPED_TRACE(t.GetTypeName().AsCString());
 
     const bool expand_pack = false;
     EXPECT_EQ(
         m_ast->GetTemplateArgumentKind(t.GetOpaqueQualType(), 0, expand_pack),
         eTemplateArgumentKindType);

lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp

 //===-- DWARFASTParserClangTests.cpp --------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "Plugins/SymbolFile/DWARF/DWARFASTParserClang.h"
 #include "Plugins/SymbolFile/DWARF/DWARFCompileUnit.h"
 #include "Plugins/SymbolFile/DWARF/DWARFDIE.h"
+#include "TestingSupport/Symbol/ClangTestUtils.h"
 #include "TestingSupport/Symbol/YAMLModuleTester.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 
 using namespace lldb;
 using namespace lldb_private;
 using namespace lldb_private::dwarf;
 
- Version:         4
             - Value:           0x0000000000000008 # DW_ATE_unsigned_char
             - Value:           0x0000000000000001
         - AbbrCode:        0x00000000
 )";
 
   YAMLModuleTester t(yamldata);
   ASSERT_TRUE((bool)t.GetDwarfUnit());
 
-  TypeSystemClang ast_ctx("dummy ASTContext", HostInfoBase::GetTargetTriple());
+  auto holder = std::make_unique<clang_utils::TypeSystemClangHolder>("ast");
+  auto &ast_ctx = *holder->GetAST();
+
   DWARFASTParserClangStub ast_parser(ast_ctx);
 
   DWARFUnit *unit = t.GetDwarfUnit();
   const DWARFDebugInfoEntry *die_first = unit->DIE().GetDIE();
   const DWARFDebugInfoEntry *die_child0 = die_first->GetFirstChild();
   const DWARFDebugInfoEntry *die_child1 = die_child0->GetSibling();
   const DWARFDebugInfoEntry *die_child2 = die_child1->GetSibling();
   const DWARFDebugInfoEntry *die_child3 = die_child2->GetSibling();
)";
   YAMLModuleTester t(yamldata);
 
   DWARFUnit *unit = t.GetDwarfUnit();
   ASSERT_NE(unit, nullptr);
   const DWARFDebugInfoEntry *cu_entry = unit->DIE().GetDIE();
   ASSERT_EQ(cu_entry->Tag(), DW_TAG_compile_unit);
   DWARFDIE cu_die(unit, cu_entry);
 
-  TypeSystemClang ast_ctx("dummy ASTContext", HostInfoBase::GetTargetTriple());
+  auto holder = std::make_unique<clang_utils::TypeSystemClangHolder>("ast");
+  auto &ast_ctx = *holder->GetAST();
   DWARFASTParserClangStub ast_parser(ast_ctx);
 
   std::vector<std::string> found_function_types;
   // The DWARF above is just a list of functions. Parse all of them to
   // extract the function types and their calling convention values.
   for (DWARFDIE func : cu_die.children()) {
     ASSERT_EQ(func.Tag(), DW_TAG_subprogram);
     SymbolContext sc;
const std::vector<std::string> expected_function_types = {
       "void ()", // invalid calling convention.
       "void ()", // DW_CC_normal -> no attribute
   };
   ASSERT_EQ(found_function_types, expected_function_types);
 }
 
 struct ExtractIntFromFormValueTest : public testing::Test {
   SubsystemRAII<FileSystem, HostInfo> subsystems;
-  TypeSystemClang ts;
+  clang_utils::TypeSystemClangHolder holder;
+  TypeSystemClang &ts;
+
   DWARFASTParserClang parser;
   ExtractIntFromFormValueTest()
-      : ts("dummy ASTContext", HostInfoBase::GetTargetTriple()), parser(ts) {}
+      : holder("dummy ASTContext"), ts(*holder.GetAST()), parser(ts) {}
 
   /// Takes the given integer value, stores it in a DWARFFormValue and then
   /// tries to extract the value back via
   /// DWARFASTParserClang::ExtractIntFromFormValue.
   /// Returns the string representation of the extracted value or the error
   /// that was returned from ExtractIntFromFormValue.
   llvm::Expected<std::string> Extract(clang::QualType qt, uint64_t value) {
     DWARFFormValue form_value;

lldb/unittests/TestingSupport/Symbol/ClangTestUtils.h

 namespace lldb_private {
 namespace clang_utils {
 inline clang::DeclarationName getDeclarationName(TypeSystemClang &ast,
                                                  llvm::StringRef name) {
   clang::IdentifierInfo &II = ast.getASTContext().Idents.get(name);
   return ast.getASTContext().DeclarationNames.getIdentifier(&II);
 }
 
-inline std::unique_ptr<TypeSystemClang> createAST() {
-  return std::make_unique<TypeSystemClang>("test ASTContext",
-                                           HostInfo::GetTargetTriple());
-}
-
 inline CompilerType createRecord(TypeSystemClang &ast, llvm::StringRef name) {
   return ast.CreateRecordType(ast.getASTContext().getTranslationUnitDecl(),
                               OptionalClangModuleID(),
                               lldb::AccessType::eAccessPublic, name, 0,
                               lldb::LanguageType::eLanguageTypeC);
 }
 
 /// Create a record with the given name and a field with the given type
 /// and name.
 inline CompilerType createRecordWithField(TypeSystemClang &ast,
                                           llvm::StringRef record_name,
                                           CompilerType field_type,
                                           llvm::StringRef field_name) {
   CompilerType t = createRecord(ast, record_name);
 
   TypeSystemClang::StartTagDeclarationDefinition(t);
   ast.AddFieldToRecordType(t, field_name, field_type,
                            lldb::AccessType::eAccessPublic, 7);
   TypeSystemClang::CompleteTagDeclarationDefinition(t);
 
   return t;
 }
 
+/// Simulates a Clang type system owned by a TypeSystemMap.
+class TypeSystemClangHolder {
+  std::shared_ptr<TypeSystemClang> m_ast;
+public:
+  TypeSystemClangHolder(const char *name)
+      : m_ast(std::make_shared<TypeSystemClang>(name,
+                                                HostInfo::GetTargetTriple())) {}
+  TypeSystemClang *GetAST() const { return m_ast.get(); }
+};
+  
 /// Constructs a TypeSystemClang that contains a single RecordDecl that contains
 /// a single FieldDecl. Utility class as this setup is a common starting point
 /// for unit test that exercise the ASTImporter.
 struct SourceASTWithRecord {
-  std::unique_ptr<TypeSystemClang> ast;
+  std::unique_ptr<TypeSystemClangHolder> holder;
+  TypeSystemClang *ast;
   CompilerType record_type;
   clang::RecordDecl *record_decl = nullptr;
   clang::FieldDecl *field_decl = nullptr;
   SourceASTWithRecord() {
-    ast = createAST();
+    holder = std::make_unique<TypeSystemClangHolder>("test ASTContext");
+    ast = holder->GetAST();
     record_type = createRecordWithField(
         *ast, "Source", ast->GetBasicType(lldb::BasicType::eBasicTypeChar),
         "a_field");
     record_decl =
         llvm::cast<clang::RecordDecl>(ClangUtil::GetAsTagDecl(record_type));
     field_decl = *record_decl->fields().begin();
     assert(field_decl);
   }
 };
 
 } // namespace clang_utils
 } // namespace lldb_private
 
 #endif