Replace stream-based error handling in the expression parser

[spyffe]

Summary

We want to do a better job presenting errors that occur when evaluating expressions. Key to this effort is getting away from a model where all errors are spat out onto a stream where the client has to take or leave all of them.

To this end, this patch adds a new class, DiagnosticManager, which contains errors produced by the compiler or by LLDB as an expression is created. The DiagnosticManager can dump itself to a log as well as to a string. Clients will (in the future) be able to filter out the errors they're interested in by ID or present subsets of these errors to the user.

This patch is not intended to change the *users* of errors – only to thread DiagnosticManagers to all the places where streams are used. I also attempt to standardize our use of errors a bit, removing trailing newlines. Going forward, I would like to make clients omit 'error:', 'warning:' etc. and exclusively pass the Severity flag.

The patch is testsuite-neutral, with modifications to one part of the MI tests because it relied on "error: error:" being erroneously printed. This patch fixes that testcase.

[jingham]

It worries me that the Diagnostic item has a "compiler specific ID" but so far as I can see there's nothing to tell me what compiler produced the ID. That means the agent consuming the diagnostic has to know a priori what compiler it is getting the diagnostic for or it won't be able to interpret it. That seems like an unnecessary restriction.

If the diagnostic manager's diagnostics were guaranteed to all come from the same compiler, you could record this in the diagnostic. Otherwise it should go in the Diagnostic itself.

[jingham]

But this is a great improvement, and other than that quibble, the code seems good.

[clayborg]

Looks good with a few minor changes as noted in inlined comments.

One question: do we want to be able to ask a DiagnosticManager object how many errors there were? Otherwise everyone has to manually iterate over them to figure out if we got any errors?

include/lldb/Expression/DiagnosticManager.h

23–28

Should we include some flag along with DiagnosticSeverity that says "please file a bug on the compiler, linker, or debugger"?

35

uint64_t for the compiler_id just to be safe and forward looking?

39

This should be inside the DiagnosticManager class as private or protected if it is the only thing that uses it. I am guessing this is only for the DiagnosticManager class?

64–66

It is probably ok to have the compiler_id be default, but "severity" shouldn't be. See comment below in the ClangDiagnosticAdaptor for more insight..

source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp

178

We should specify eDiagnosticSeverityError here to be clear. I believe the severity should not be a default argument to keep the code easier to read.

[spyffe]

Many of Greg's concerns reflect the fact that we're not giving people access to the raw Diagnostic objects and instead optimistically designing API. Upon reflection, I would rather give people access to a const DiagnosticList & and only add mutators when code actually needs them. This, and responses to Jim's and Greg's comments, will be in the next iteration of this patch.

include/lldb/Expression/DiagnosticManager.h

35

I would not do this, simply because I doubt that there will be 4 billion unique diagnostics and because there is no need for binary compatibility of any sort here.

As Jim suggested, though, an origin field would be useful.

39

There are functions that take and return these, namely GetAllDiagnosticsAfter and AppendDiagnostics.

64–66

Good point. I will fix this.

source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp

178

You're right. I will fix this.

[ldrumm]

Overall this patch is great cleanup!

However, see my comments inline. Most are simply minor implementation details.

Also, the new code introduces some trailing whitespace, and has is inconsistent between void prototype();, void prototype (); and callfunc();, callfunc (); so it may be worth running clang-format-diff` on the changes.

include/lldb/Expression/DiagnosticManager.h

84

I think it might be helpful to have a comment describing the format of the returned string. The implementation joins them with newlines, but this is non-obvious.

source/Expression/DiagnosticManager.cpp

51

Would it be better to batch these, and then dump a single string to the log in one go - akin to what Greg suggested in this diff?
In fact, as you already have the GetString method, you could maybe do:

void
DiagnosticManager::Dump(Log *log)
{
    if (!log)
        return;
    log->PutCString(GetString().c_str());
}

Although the newlines will be different in the current implementation.

You could therefore change the protoype for GetString

cpp
std::string
DiagnosticManager::GetString(char separator='\n')
{
std::string
DiagnosticManager::GetString(char separator)
{
    std::string ret;
    
    for (Diagnostic &diagnostic : m_diagnostics)
    {
        ret.append(diagnostic.message);
        ret.push_back(separator);
    }
    
    return ret;
}

source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp

491

num_errors looks to be unsigned I believe %d should be %u

source/Target/Process.cpp

5481

num_resumes is uint32_t : %d -> PRIu32

5498

num_resumes is uint32_t : %d -> PRIu32

[spyffe]

Thanks for the comments, Luke! I have responded to your changes, will run clang-format, and will then update this diff.

include/lldb/Expression/DiagnosticManager.h

84

Very true. Will do.

source/Expression/DiagnosticManager.cpp

51

Will do. Thanks. The only difference with the log is the trailing newline. Maybe I'll just manually remove that from the output of GetString.

source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp

491

Will fix, thanks.

source/Target/Process.cpp

5481

Will fix.

5498

Will fix.

[spyffe]

Applied previous comments as discussed before.
Ran ./llvm/tools/clang/tools/clang-format/clang-format-diff.py -b ./llvm-build/Debug+Asserts/x86_64/bin/clang-format -i

[clayborg]

Just change the "origin" variable over to use DiagnosticOrigin as the type and this is good to go.

include/lldb/Expression/DiagnosticManager.h

43

The type of this should be DiagnosticOrigin, not uint32_t

[clayborg]

After you change "origin" to be a DiagnosticOrigin this is ready.

[spyffe]

Thanks. I will apply your suggestion.

include/lldb/Expression/DiagnosticManager.h

43

Yeah, since we're not trying to maintain binary compatibility, I agree.

[jingham]

LGTM

[ldrumm]

I haven't had a chance to try this out (at EuroLLVM) but looks good.

[Eugene.Zelenko]

Seems to be part of r263859.

include/lldb/Expression/DiagnosticManager.h

+//===-- DiagnosticManager.h -------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef lldb_DiagnosticManager_h
+#define lldb_DiagnosticManager_h
+
+#include "lldb/lldb-types.h"
+
+#include <string>
+#include <vector>
+
+namespace lldb_private
+{
+
+enum DiagnosticOrigin
+{
+    eDiagnosticOriginUnknown = 0,
+    eDiagnosticOriginLLDB,
+    eDiagnosticOriginClang,
+    eDiagnosticOriginGo,
+    eDiagnosticOriginSwift,
+    eDiagnosticOriginLLVM
+};
+
+enum DiagnosticSeverity
+{
+    eDiagnosticSeverityError,
+    eDiagnosticSeverityWarning,
+    eDiagnosticSeverityRemark
+};
+
+const uint32_t LLDB_INVALID_COMPILER_ID = UINT32_MAX;
+
+struct Diagnostic
+{
+    std::string message;
+    uint32_t origin;      // from DiagnosticOrigin
+    uint32_t compiler_id; // Compiler-specific diagnostic ID
+    DiagnosticSeverity severity;
+};
+
+typedef std::vector<Diagnostic> DiagnosticList;
+
+class DiagnosticManager
+{
+public:
+    void
+    Clear()
+    {
+        m_diagnostics.clear();
+    }
+
+    const DiagnosticList &
+    Diagnostics()
+    {
+        return m_diagnostics;
+    }
+
+    void
+    AddDiagnostic(const char *message, DiagnosticSeverity severity, DiagnosticOrigin origin,
+                  uint32_t compiler_id = LLDB_INVALID_COMPILER_ID)
+    {
+        m_diagnostics.push_back({std::string(message), origin, compiler_id, severity});
+    }
+
+    size_t
+    Printf(DiagnosticSeverity severity, const char *format, ...) __attribute__((format(printf, 3, 4)));
+    size_t
+    PutCString(DiagnosticSeverity severity, const char *cstr);
+
+    void
+    AppendMessageToDiagnostic(const char *cstr)
+    {
+        if (m_diagnostics.size())
+        {
+            m_diagnostics.back().message.push_back('\n');
+            m_diagnostics.back().message.append(cstr);
+        }
+    }
+
+    // Returns a string containing errors in this format:
+    //
+    // "error: error text\n
+    // warning: warning text\n
+    // remark text\n"
+    std::string
+    GetString(char separator = '\n');
+
+    void
+    Dump(Log *log);
+
+private:
+    DiagnosticList m_diagnostics;
+};
+}
+
+#endif /* lldb_DiagnosticManager_h */

include/lldb/Expression/ExpressionParser.h

     /// Parse a single expression and convert it to IR using Clang.  Don't
     /// wrap the expression in anything at all.
     ///
-    /// @param[in] stream
+    /// @param[in] diagnostic_manager
     ///     The stream to print errors to.
     ///
     /// @return

     ///     success.
     //------------------------------------------------------------------
     virtual unsigned
-    Parse (Stream &stream) = 0;
-    
+    Parse(DiagnosticManager &diagnostic_manager) = 0;
     //------------------------------------------------------------------
     /// Ready an already-parsed expression for execution, possibly
     /// evaluating it statically.

include/lldb/Expression/FunctionCaller.h

     //------------------------------------------------------------------
     /// Compile the wrapper function
     ///
-    /// @param[in] errors
-    ///     The stream to print parser errors to.
+    /// @param[in] diagnostic_manager
+    ///     The diagnostic manager to report parser errors to.
     ///
     /// @return
     ///     The number of errors.
     //------------------------------------------------------------------
     virtual unsigned
-    CompileFunction (Stream &errors) = 0;
-    
+    CompileFunction(DiagnosticManager &diagnostic_manager) = 0;
     //------------------------------------------------------------------
-    /// Insert the default function wrapper and its default argument struct  
+    /// Insert the default function wrapper and its default argument struct
     ///
     /// @param[in] exe_ctx
     ///     The execution context to insert the function and its arguments

     ///     be LLDB_INVALID_ADDRESS; if it is, a new structure is allocated
     ///     and args_addr_ref is pointed to it.
     ///
-    /// @param[in] errors
-    ///     The stream to write errors to.
+    /// @param[in] diagnostic_manager
+    ///     The diagnostic manager to report errors to.
     ///
     /// @return
     ///     True on success; false otherwise.
     //------------------------------------------------------------------
     bool
-    InsertFunction (ExecutionContext &exe_ctx,
-                    lldb::addr_t &args_addr_ref,
-                    Stream &errors);
+    InsertFunction(ExecutionContext &exe_ctx, lldb::addr_t &args_addr_ref, DiagnosticManager &diagnostic_manager);
 
     //------------------------------------------------------------------
     /// Insert the default function wrapper (using the JIT)

     ///     The execution context to insert the function and its arguments
     ///     into.
     ///
-    /// @param[in] errors
-    ///     The stream to write errors to.
+    /// @param[in] diagnostic_manager
+    ///     The diagnostic manager to report errors to.
     ///
     /// @return
     ///     True on success; false otherwise.
     //------------------------------------------------------------------
-    bool WriteFunctionWrapper (ExecutionContext &exe_ctx, 
-                               Stream &errors);
-    
+    bool
+    WriteFunctionWrapper(ExecutionContext &exe_ctx, DiagnosticManager &diagnostic_manager);
     //------------------------------------------------------------------
-    /// Insert the default function argument struct  
+    /// Insert the default function argument struct
     ///
     /// @param[in] exe_ctx
     ///     The execution context to insert the function and its arguments

     ///     be LLDB_INVALID_ADDRESS; if it is, a new structure is allocated
     ///     and args_addr_ref is pointed to it.
     ///
-    /// @param[in] errors
-    ///     The stream to write errors to.
+    /// @param[in] diagnostic_manager
+    ///     The diagnostic manager to report errors to.
     ///
     /// @return
     ///     True on success; false otherwise.
     //------------------------------------------------------------------
-    bool WriteFunctionArguments (ExecutionContext &exe_ctx, 
-                                 lldb::addr_t &args_addr_ref, 
-                                 Stream &errors);
-    
+    bool
+    WriteFunctionArguments(ExecutionContext &exe_ctx, lldb::addr_t &args_addr_ref,
+                           DiagnosticManager &diagnostic_manager);
     //------------------------------------------------------------------
     /// Insert an argument struct with a non-default function address and
     /// non-default argument values

     /// @param[in] arg_values
     ///     The values of the function's arguments.
     ///
-    /// @param[in] errors
-    ///     The stream to write errors to.
+    /// @param[in] diagnostic_manager
+    ///     The diagnostic manager to report errors to.
     ///
     /// @return
     ///     True on success; false otherwise.
     //------------------------------------------------------------------
-    bool WriteFunctionArguments (ExecutionContext &exe_ctx, 
-                                 lldb::addr_t &args_addr_ref, 
-                                 ValueList &arg_values,
-                                 Stream &errors);
+    bool
+    WriteFunctionArguments(ExecutionContext &exe_ctx, lldb::addr_t &args_addr_ref, ValueList &arg_values,
+                           DiagnosticManager &diagnostic_manager);
 
     //------------------------------------------------------------------
     /// Run the function this FunctionCaller was created with.

     ///     for deallocating it.  And if passed in with a value other than LLDB_INVALID_ADDRESS,
     ///     this should point to an already allocated structure with the values already written.
     ///
-    /// @param[in] errors
-    ///     Errors will be written here if there are any.
+    /// @param[in] diagnostic_manager
+    ///     The diagnostic manager to report errors to.
     ///
     /// @param[in] options
     ///     The options for this expression execution.

     ///     Returns one of the ExpressionResults enum indicating function call status.
     //------------------------------------------------------------------
     lldb::ExpressionResults
-    ExecuteFunction(ExecutionContext &exe_ctx, 
-                    lldb::addr_t *args_addr_ptr, 
-                    const EvaluateExpressionOptions &options,
-                    Stream &errors,
-                    Value &results);
-    
+    ExecuteFunction(ExecutionContext &exe_ctx, lldb::addr_t *args_addr_ptr, const EvaluateExpressionOptions &options,
+                    DiagnosticManager &diagnostic_manager, Value &results);
+
     //------------------------------------------------------------------
     /// Get a thread plan to run the function this FunctionCaller was created with.
     ///

     /// @param[in] args_addr
     ///     The address of the argument struct.
     ///
-    /// @param[in] errors
-    ///     The stream to write errors to.
+    /// @param[in] diagnostic_manager
+    ///     The diagnostic manager to report errors to.
     ///
     /// @param[in] stop_others
     ///     True if other threads should pause during execution.

     ///     A ThreadPlan shared pointer for executing the function.
     //------------------------------------------------------------------
     lldb::ThreadPlanSP
-    GetThreadPlanToCallFunction (ExecutionContext &exe_ctx, 
-                                 lldb::addr_t args_addr,
-                                 const EvaluateExpressionOptions &options,
-                                 Stream &errors);
-    
+    GetThreadPlanToCallFunction(ExecutionContext &exe_ctx, lldb::addr_t args_addr,
+                                const EvaluateExpressionOptions &options, DiagnosticManager &diagnostic_manager);
+
     //------------------------------------------------------------------
     /// Get the result of the function from its struct
     ///

include/lldb/Expression/IRDynamicChecks.h

     /// Install the utility functions into a process.  This binds the
     /// instance of DynamicCheckerFunctions to that process.
     ///
-    /// @param[in] error_stream
-    ///     A stream to print errors on.
+    /// @param[in] diagnostic_manager
+    ///     A diagnostic manager to report errors to.
     ///
     /// @param[in] exe_ctx
     ///     The execution context to install the functions into.

     ///     True on success; false on failure, or if the functions have
     ///     already been installed.
     //------------------------------------------------------------------
-    bool Install (Stream &error_stream,
-                  ExecutionContext &exe_ctx);
-    
-    bool DoCheckersExplainStop (lldb::addr_t addr, Stream &message);
-    
+    bool
+    Install(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx);
+    bool
+    DoCheckersExplainStop(lldb::addr_t addr, Stream &message);
+
     std::unique_ptr<UtilityFunction> m_valid_pointer_check;
     std::unique_ptr<UtilityFunction> m_objc_object_check;
 };

include/lldb/Expression/LLVMUserExpression.h

 class LLVMUserExpression : public UserExpression
 {
   public:
-    LLVMUserExpression(ExecutionContextScope &exe_scope,
-                       const char *expr,
-                       const char *expr_prefix,
-                       lldb::LanguageType language,
-                       ResultType desired_type,
-                       const EvaluateExpressionOptions &options);
-    ~LLVMUserExpression() override;
+      LLVMUserExpression(ExecutionContextScope &exe_scope, const char *expr, const char *expr_prefix,
+                         lldb::LanguageType language, ResultType desired_type,
+                         const EvaluateExpressionOptions &options);
+      ~LLVMUserExpression() override;
 
-    lldb::ExpressionResults Execute(Stream &error_stream,
-                                    ExecutionContext &exe_ctx,
-                                    const EvaluateExpressionOptions &options,
-                                    lldb::UserExpressionSP &shared_ptr_to_me,
-                                    lldb::ExpressionVariableSP &result) override;
+      lldb::ExpressionResults
+      Execute(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+              const EvaluateExpressionOptions &options, lldb::UserExpressionSP &shared_ptr_to_me,
+              lldb::ExpressionVariableSP &result) override;
 
-    bool FinalizeJITExecution(Stream &error_stream,
-                              ExecutionContext &exe_ctx,
-                              lldb::ExpressionVariableSP &result,
-                              lldb::addr_t function_stack_bottom = LLDB_INVALID_ADDRESS,
-                              lldb::addr_t function_stack_top = LLDB_INVALID_ADDRESS) override;
+      bool
+      FinalizeJITExecution(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
 
       bool
       CanInterpret() override
       {
           return m_can_interpret;
     }
 
     //------------------------------------------------------------------

 
     lldb::ModuleSP GetJITModule() override;
 
-  protected:
-    virtual void ScanContext(ExecutionContext &exe_ctx, lldb_private::Error &err) = 0;
+    virtual void
+    ScanContext(ExecutionContext &exe_ctx, lldb_private::Error &err) = 0;
 
-    bool PrepareToExecuteJITExpression(Stream &error_stream, ExecutionContext &exe_ctx, lldb::addr_t &struct_address);
+    bool
+    PrepareToExecuteJITExpression(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+                                  lldb::addr_t &struct_address);
 
     virtual bool
-    AddArguments (ExecutionContext &exe_ctx,
-                  std::vector<lldb::addr_t> &args,
-                  lldb::addr_t struct_address,
-                  Stream &error_stream) = 0;
+    AddArguments(ExecutionContext &exe_ctx, std::vector<lldb::addr_t> &args, lldb::addr_t struct_address,
+                 DiagnosticManager &diagnostic_manager) = 0;
 
-
     lldb::addr_t m_stack_frame_bottom; ///< The bottom of the allocated stack frame.
     lldb::addr_t m_stack_frame_top;    ///< The top of the allocated stack frame.
 

include/lldb/Expression/UserExpression.h

     //------------------------------------------------------------------
     /// Parse the expression
     ///
-    /// @param[in] error_stream
-    ///     A stream to print parse errors and warnings to.
+    /// @param[in] diagnostic_manager
+    ///     A diagnostic manager to report parse errors and warnings to.
     ///
     /// @param[in] exe_ctx
     ///     The execution context to use when looking up entities that

     ///     True on success (no errors); false otherwise.
     //------------------------------------------------------------------
     virtual bool
-    Parse (Stream &error_stream,
-           ExecutionContext &exe_ctx,
-           lldb_private::ExecutionPolicy execution_policy,
-           bool keep_result_in_memory,
-           bool generate_debug_info) = 0;
+    Parse(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+          lldb_private::ExecutionPolicy execution_policy, bool keep_result_in_memory, bool generate_debug_info) = 0;
 
     virtual bool CanInterpret() = 0;
 

     //------------------------------------------------------------------
     /// Execute the parsed expression
     ///
-    /// @param[in] error_stream
-    ///     A stream to print errors to.
+    /// @param[in] diagnostic_manager
+    ///     A diagnostic manager to report errors to.
     ///
     /// @param[in] exe_ctx
     ///     The execution context to use when looking up entities that

     /// @return
     ///     A Process::Execution results value.
     //------------------------------------------------------------------
-    virtual lldb::ExpressionResults Execute(Stream &error_stream, ExecutionContext &exe_ctx,
-                                            const EvaluateExpressionOptions &options,
-                                            lldb::UserExpressionSP &shared_ptr_to_me,
-                                            lldb::ExpressionVariableSP &result) = 0;
+    virtual lldb::ExpressionResults
+    Execute(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx, const EvaluateExpressionOptions &options,
+            lldb::UserExpressionSP &shared_ptr_to_me, lldb::ExpressionVariableSP &result) = 0;
 
     //------------------------------------------------------------------
     /// Apply the side effects of the function to program state.
     ///
-    /// @param[in] error_stream
-    ///     A stream to print errors to.
+    /// @param[in] diagnostic_manager
+    ///     A diagnostic manager to report errors to.
     ///
     /// @param[in] exe_ctx
     ///     The execution context to use when looking up entities that

     /// @return
     ///     A Process::Execution results value.
     //------------------------------------------------------------------
-    virtual bool FinalizeJITExecution(Stream &error_stream, ExecutionContext &exe_ctx,
-                                      lldb::ExpressionVariableSP &result,
-                                      lldb::addr_t function_stack_bottom = LLDB_INVALID_ADDRESS,
-                                      lldb::addr_t function_stack_top = LLDB_INVALID_ADDRESS) = 0;
+    virtual bool
+    FinalizeJITExecution(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+                         lldb::ExpressionVariableSP &result, lldb::addr_t function_stack_bottom = LLDB_INVALID_ADDRESS,
 
     //------------------------------------------------------------------
     /// Return the string that the parser should parse.

include/lldb/Expression/UtilityFunction.h

     //------------------------------------------------------------------
     /// Install the utility function into a process
     ///
-    /// @param[in] error_stream
-    ///     A stream to print parse errors and warnings to.
+    /// @param[in] diagnostic_manager
+    ///     A diagnostic manager to print parse errors and warnings to.
     ///
     /// @param[in] exe_ctx
     ///     The execution context to install the utility function to.

     ///     True on success (no errors); false otherwise.
     //------------------------------------------------------------------
     virtual bool
-    Install (Stream &error_stream, ExecutionContext &exe_ctx) = 0;
-    
+    Install(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx) = 0;
     //------------------------------------------------------------------
     /// Check whether the given PC is inside the function
     ///

include/lldb/Target/Process.h

     //------------------------------------------------------------------
     lldb::StateType
     GetState ();
-    
     lldb::ExpressionResults
-    RunThreadPlan (ExecutionContext &exe_ctx,    
-                    lldb::ThreadPlanSP &thread_plan_sp,
-                    const EvaluateExpressionOptions &options,
-                    Stream &errors);
+    RunThreadPlan(ExecutionContext &exe_ctx, lldb::ThreadPlanSP &thread_plan_sp,
+                  const EvaluateExpressionOptions &options, DiagnosticManager &diagnostic_manager);
 
     static const char *
-    ExecutionResultAsCString (lldb::ExpressionResults result);
+    ExecutionResultAsCString(lldb::ExpressionResults result);
 
     void
     GetStatus (Stream &ostrm);

include/lldb/lldb-forward.h

 class   DataExtractor;
 class   Debugger;
 class   Declaration;
+class   DiagnosticManager;
 class   Disassembler;
 class   DumpValueObjectOptions;
 class   DynamicCheckerFunctions;

packages/Python/lldbsuite/test/tools/lldb-mi/variable/TestMiVar.py

 
         # Print non-existant variable
         self.runCmd("-var-create var1 * undef")
-        self.expect("\^error,msg=\"error: error: use of undeclared identifier \'undef\'\\\\nerror: 1 errors parsing expression\\\\n\"")
+        self.expect("\^error,msg=\"error: use of undeclared identifier \'undef\'\\\\nerror: 1 error parsing expression\\\\n\"")
         self.runCmd("-data-evaluate-expression undef")
-        self.expect("\^error,msg=\"error: use of undeclared identifier \'undef\'\\\\nerror: 1 errors parsing expression\\\\n\"")
+        self.expect("\^error,msg=\"use of undeclared identifier \'undef\'\\\\nerror: 1 error parsing expression\\\\n\"")
 
         # Print global "g_MyVar", modify, delete and create again
         self.runCmd("-data-evaluate-expression g_MyVar")

source/Breakpoint/BreakpointLocation.cpp

 #include "lldb/Core/Module.h"
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/ValueObject.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/ExpressionVariable.h"
 #include "lldb/Expression/UserExpression.h"
 #include "lldb/Symbol/CompileUnit.h"

         m_user_expression_sp.reset();
         return false;
     }
-    
-    if (condition_hash != m_condition_hash ||
-        !m_user_expression_sp ||
-        !m_user_expression_sp->MatchesContext(exe_ctx))
+    DiagnosticManager diagnostics;
+
+    if (condition_hash != m_condition_hash || !m_user_expression_sp || !m_user_expression_sp->MatchesContext(exe_ctx))
     {
         LanguageType language = eLanguageTypeUnknown;
         // See if we can figure out the language from the frame, otherwise use the default language:

             return true;
         }
 
-        StreamString errors;
-        
-        if (!m_user_expression_sp->Parse(errors,
-                                         exe_ctx,
-                                         eExecutionPolicyOnlyWhenNeeded,
-                                         true,
-                                         false))
+        if (!m_user_expression_sp->Parse(diagnostics, exe_ctx, eExecutionPolicyOnlyWhenNeeded, true, false))
         {
             error.SetErrorStringWithFormat("Couldn't parse conditional expression:\n%s",
-                                           errors.GetData());
+                                           diagnostics.GetString().c_str());
             m_user_expression_sp.reset();
             return false;
         }
-        
         m_condition_hash = condition_hash;
     }
 

     options.SetUnwindOnError(true);
     options.SetIgnoreBreakpoints(true);
     options.SetTryAllThreads(true);
-    
     Error expr_error;
-    
-    StreamString execution_errors;
-    
+    diagnostics.Clear();
     ExpressionVariableSP result_variable_sp;
-    
     ExpressionResults result_code =
-    m_user_expression_sp->Execute(execution_errors,
-                                  exe_ctx,
-                                  options,
-                                  m_user_expression_sp,
-                                  result_variable_sp);
-    
+        m_user_expression_sp->Execute(diagnostics, exe_ctx, options, m_user_expression_sp, result_variable_sp);
+
     bool ret;
     
     if (result_code == eExpressionCompleted)

     else
     {
         ret = false;
-        error.SetErrorStringWithFormat("Couldn't execute expression:\n%s", execution_errors.GetData());
+        error.SetErrorStringWithFormat("Couldn't execute expression:\n%s", diagnostics.GetString().c_str());
     }
-    
     return ret;
 }
 

source/Expression/DiagnosticManager.cpp

+//===-- DiagnosticManager.cpp -----------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "lldb/Expression/DiagnosticManager.h"
+#include "lldb/Core/Log.h"
+#include "lldb/Core/StreamString.h"
+
+using namespace lldb_private;
+
+void
+DiagnosticManager::Dump(Log *log)
+{
+    if (!log)
+        return;
+
+    std::string str = GetString();
+
+    // GetString() puts a separator after each diagnostic.
+    // We want to remove the last '\n' because log->PutCString will add one for us.
+
+    if (str.size() && str.back() == '\n')
+    {
+        str.pop_back();
+    }
+
+    log->PutCString(str.c_str());
+}
+
+static const char *
+StringForSeverity(DiagnosticSeverity severity)
+{
+    switch (severity)
+    {
+        // this should be exhaustive
+        case lldb_private::eDiagnosticSeverityError:
+            return "error: ";
+        case lldb_private::eDiagnosticSeverityWarning:
+            return "warning: ";
+        case lldb_private::eDiagnosticSeverityRemark:
+            return "";
+    }
+}
+
+std::string
+DiagnosticManager::GetString(char separator)
+{
+    std::string ret;
+
+    for (const Diagnostic &diagnostic : Diagnostics())
+    {
+        ret.append(StringForSeverity(diagnostic.severity));
+        ret.append(diagnostic.message);
+        ret.push_back(separator);
+    }
+
+    return ret;
+}
+
+size_t
+DiagnosticManager::Printf(DiagnosticSeverity severity, const char *format, ...)
+{
+    StreamString ss;
+
+    va_list args;
+    va_start(args, format);
+    size_t result = ss.PrintfVarArg(format, args);
+    va_end(args);
+
+    AddDiagnostic(ss.GetData(), severity, eDiagnosticOriginLLDB);
+
+    return result;
+}
+
+size_t
+DiagnosticManager::PutCString(DiagnosticSeverity severity, const char *cstr)
+{
+    if (!cstr)
+        return 0;
+    AddDiagnostic(cstr, severity, eDiagnosticOriginLLDB);
+    return strlen(cstr);
+}

source/Expression/FunctionCaller.cpp

 // Other libraries and framework includes
 
 // Project includes
+#include "lldb/Expression/FunctionCaller.h"
 #include "lldb/Core/DataExtractor.h"
 #include "lldb/Core/Log.h"
 #include "lldb/Core/Module.h"
 #include "lldb/Core/State.h"
 #include "lldb/Core/ValueObject.h"
 #include "lldb/Core/ValueObjectList.h"
-#include "lldb/Expression/FunctionCaller.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/IRExecutionUnit.h"
 #include "lldb/Interpreter/CommandReturnObject.h"
 #include "lldb/Symbol/Function.h"

         lldb::ModuleSP jit_module_sp (m_jit_module_wp.lock());
         if (jit_module_sp)
             process_sp->GetTarget().GetImages().Remove(jit_module_sp);
-    }    
+    }
 }
 
 bool
-FunctionCaller::WriteFunctionWrapper (ExecutionContext &exe_ctx, Stream &errors)
+FunctionCaller::WriteFunctionWrapper(ExecutionContext &exe_ctx, DiagnosticManager &diagnostic_manager)
 {
     Process *process = exe_ctx.GetProcessPtr();
 

 }
 
 bool
-FunctionCaller::WriteFunctionArguments (ExecutionContext &exe_ctx, lldb::addr_t &args_addr_ref, Stream &errors)
+FunctionCaller::WriteFunctionArguments(ExecutionContext &exe_ctx, lldb::addr_t &args_addr_ref,
+                                       DiagnosticManager &diagnostic_manager)
 {
-    return WriteFunctionArguments(exe_ctx, args_addr_ref, m_arg_values, errors);
+    return WriteFunctionArguments(exe_ctx, args_addr_ref, m_arg_values, diagnostic_manager);
 }
 
 // FIXME: Assure that the ValueList we were passed in is consistent with the one that defined this function.
 
 bool
-FunctionCaller::WriteFunctionArguments (ExecutionContext &exe_ctx, 
-                                       lldb::addr_t &args_addr_ref, 
-                                       ValueList &arg_values,
-                                       Stream &errors)
+FunctionCaller::WriteFunctionArguments(ExecutionContext &exe_ctx, lldb::addr_t &args_addr_ref, ValueList &arg_values,
+                                       DiagnosticManager &diagnostic_manager)
 {
     // All the information to reconstruct the struct is provided by the
     // StructExtractor.
     if (!m_struct_valid)
     {
-        errors.Printf("Argument information was not correctly parsed, so the function cannot be called.");
+        diagnostic_manager.PutCString(
+            eDiagnosticSeverityError,
+            "Argument information was not correctly parsed, so the function cannot be called.");
         return false;
     }
-        
     Error error;
     lldb::ExpressionResults return_value = lldb::eExpressionSetupError;
 

     // FIXME: We will need to extend this for Variadic functions.
 
     Error value_error;
-    
     size_t num_args = arg_values.GetSize();
     if (num_args != m_arg_values.GetSize())
     {
-        errors.Printf ("Wrong number of arguments - was: %" PRIu64 " should be: %" PRIu64 "", (uint64_t)num_args, (uint64_t)m_arg_values.GetSize());
+        diagnostic_manager.Printf(eDiagnosticSeverityError,
+                                  "Wrong number of arguments - was: %" PRIu64 " should be: %" PRIu64 "",
+                                  (uint64_t)num_args, (uint64_t)m_arg_values.GetSize());
         return false;
     }
-    
     for (size_t i = 0; i < num_args; i++)
     {
         // FIXME: We should sanity check sizes.

 }
 
 bool
-FunctionCaller::InsertFunction (ExecutionContext &exe_ctx, lldb::addr_t &args_addr_ref, Stream &errors)
+FunctionCaller::InsertFunction(ExecutionContext &exe_ctx, lldb::addr_t &args_addr_ref,
+                               DiagnosticManager &diagnostic_manager)
 {
-    if (CompileFunction(errors) != 0)
+    if (CompileFunction(diagnostic_manager) != 0)
         return false;
-    if (!WriteFunctionWrapper(exe_ctx, errors))
+    if (!WriteFunctionWrapper(exe_ctx, diagnostic_manager))
         return false;
-    if (!WriteFunctionArguments(exe_ctx, args_addr_ref, errors))
+    if (!WriteFunctionArguments(exe_ctx, args_addr_ref, diagnostic_manager))
         return false;
 
-    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_STEP));
+    Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
     if (log)
         log->Printf ("Call Address: 0x%" PRIx64 " Struct Address: 0x%" PRIx64 ".\n", m_jit_start_addr, args_addr_ref);
         

 }
 
 lldb::ThreadPlanSP
-FunctionCaller::GetThreadPlanToCallFunction (ExecutionContext &exe_ctx, 
-                                            lldb::addr_t args_addr,
+FunctionCaller::GetThreadPlanToCallFunction(ExecutionContext &exe_ctx, lldb::addr_t args_addr,
                                             const EvaluateExpressionOptions &options,
-                                            Stream &errors)
+                                            DiagnosticManager &diagnostic_manager)
 {
-    Log *log(lldb_private::GetLogIfAnyCategoriesSet (LIBLLDB_LOG_EXPRESSIONS | LIBLLDB_LOG_STEP));
-    
+    Log *log(lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_EXPRESSIONS | LIBLLDB_LOG_STEP));
     if (log)
         log->Printf("-- [FunctionCaller::GetThreadPlanToCallFunction] Creating thread plan to call function \"%s\" --", m_name.c_str());
     

     Thread *thread = exe_ctx.GetThreadPtr();
     if (thread == NULL)
     {
-        errors.Printf("Can't call a function without a valid thread.");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "Can't call a function without a valid thread.");
         return NULL;
     }
 

 }
 
 lldb::ExpressionResults
-FunctionCaller::ExecuteFunction(
-        ExecutionContext &exe_ctx, 
-        lldb::addr_t *args_addr_ptr,
-        const EvaluateExpressionOptions &options,
-        Stream &errors, 
-        Value &results)
+FunctionCaller::ExecuteFunction(ExecutionContext &exe_ctx, lldb::addr_t *args_addr_ptr,
+                                const EvaluateExpressionOptions &options, DiagnosticManager &diagnostic_manager,
+                                Value &results)
 {
     lldb::ExpressionResults return_value = lldb::eExpressionSetupError;
-    
     // FunctionCaller::ExecuteFunction execution is always just to get the result.  Do make sure we ignore
     // breakpoints, unwind on error, and don't try to debug it.
     EvaluateExpressionOptions real_options = options;

         args_addr = *args_addr_ptr;
     else
         args_addr = LLDB_INVALID_ADDRESS;
-        
-    if (CompileFunction(errors) != 0)
+    if (CompileFunction(diagnostic_manager) != 0)
         return lldb::eExpressionSetupError;
-    
     if (args_addr == LLDB_INVALID_ADDRESS)
     {
-        if (!InsertFunction(exe_ctx, args_addr, errors))
+        if (!InsertFunction(exe_ctx, args_addr, diagnostic_manager))
             return lldb::eExpressionSetupError;
     }
 

 
     if (log)
         log->Printf("== [FunctionCaller::ExecuteFunction] Executing function \"%s\" ==", m_name.c_str());
-    
-    lldb::ThreadPlanSP call_plan_sp = GetThreadPlanToCallFunction (exe_ctx,
-                                                                   args_addr,
-                                                                   real_options,
-                                                                   errors);
+    lldb::ThreadPlanSP call_plan_sp = GetThreadPlanToCallFunction(exe_ctx, args_addr, real_options, diagnostic_manager);
     if (!call_plan_sp)
         return lldb::eExpressionSetupError;
-        
     // We need to make sure we record the fact that we are running an expression here
     // otherwise this fact will fail to be recorded when fetching an Objective-C object description
     if (exe_ctx.GetProcessPtr())
         exe_ctx.GetProcessPtr()->SetRunningUserExpression(true);
-    
-    return_value = exe_ctx.GetProcessRef().RunThreadPlan (exe_ctx,
-                                                          call_plan_sp,
-                                                          real_options,
-                                                          errors);
-    
+    return_value = exe_ctx.GetProcessRef().RunThreadPlan(exe_ctx, call_plan_sp, real_options, diagnostic_manager);
+
     if (log)
     {
         if (return_value != lldb::eExpressionCompleted)

source/Expression/IRDynamicChecks.cpp

 DynamicCheckerFunctions::~DynamicCheckerFunctions() = default;
 
 bool
-DynamicCheckerFunctions::Install(Stream &error_stream,
-                                 ExecutionContext &exe_ctx)
+DynamicCheckerFunctions::Install(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx)
 {
     Error error;
     m_valid_pointer_check.reset(exe_ctx.GetTargetRef().GetUtilityFunctionForLanguage(g_valid_pointer_check_text,

                                                                                      error));
     if (error.Fail())
         return false;
-        
-    if (!m_valid_pointer_check->Install(error_stream, exe_ctx))
+    if (!m_valid_pointer_check->Install(diagnostic_manager, exe_ctx))
         return false;
 
     Process *process = exe_ctx.GetProcessPtr();

         {
             m_objc_object_check.reset(objc_language_runtime->CreateObjectChecker(VALID_OBJC_OBJECT_CHECK_NAME));
 
-            if (!m_objc_object_check->Install(error_stream, exe_ctx))
+            if (!m_objc_object_check->Install(diagnostic_manager, exe_ctx))
                 return false;
         }
     }

source/Expression/IRInterpreter.cpp

 //
 //===----------------------------------------------------------------------===//
 
+#include "lldb/Expression/IRInterpreter.h"
 #include "lldb/Core/ConstString.h"
 #include "lldb/Core/DataExtractor.h"
 #include "lldb/Core/Error.h"
 #include "lldb/Core/Log.h"
+#include "lldb/Core/Module.h"
 #include "lldb/Core/ModuleSpec.h"
-#include "lldb/Core/Module.h"
 #include "lldb/Core/Scalar.h"
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/ValueObject.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/IRExecutionUnit.h"
 #include "lldb/Expression/IRMemoryMap.h"
-#include "lldb/Expression/IRInterpreter.h"
 #include "lldb/Host/Endian.h"
 
 #include "lldb/Target/ABI.h"

                 }
                 lldb_private::Address funcAddr(I.ULongLong(LLDB_INVALID_ADDRESS));
 
-                lldb_private::StreamString error_stream;
+                lldb_private::DiagnosticManager diagnostics;
                 lldb_private::EvaluateExpressionOptions options;
 
                 // We generally receive a function pointer which we must dereference

                 llvm::ArrayRef<lldb_private::ABI::CallArgument> args(rawArgs, numArgs);
 
                 // Setup a thread plan to call the target function
-                lldb::ThreadPlanSP call_plan_sp
-                (
-                    new lldb_private::ThreadPlanCallFunctionUsingABI
-                    (
-                        exe_ctx.GetThreadRef(),
-                        funcAddr,
-                        *prototype,
-                        *returnType,
-                        args,
-                        options
-                    )
-                );
+                lldb::ThreadPlanSP call_plan_sp(new lldb_private::ThreadPlanCallFunctionUsingABI(
+                    exe_ctx.GetThreadRef(), funcAddr, *prototype, *returnType, args, options));
 
                 // Check if the plan is valid
-                if (!call_plan_sp || !call_plan_sp->ValidatePlan(&error_stream))
+                lldb_private::StreamString ss;
+                if (!call_plan_sp || !call_plan_sp->ValidatePlan(&ss))
                 {
                     error.SetErrorToGenericError();
-                    error.SetErrorStringWithFormat("unable to make ThreadPlanCallFunctionUsingABI for 0x%llx", I.ULongLong());
+                    error.SetErrorStringWithFormat("unable to make ThreadPlanCallFunctionUsingABI for 0x%llx",
+                                                   I.ULongLong());
                     return false;
                 }
 
                 exe_ctx.GetProcessPtr()->SetRunningUserExpression(true);
 
                 // Execute the actual function call thread plan
-                lldb::ExpressionResults res = exe_ctx.GetProcessRef().RunThreadPlan(exe_ctx, call_plan_sp, options, error_stream);
+                lldb::ExpressionResults res =
+                    exe_ctx.GetProcessRef().RunThreadPlan(exe_ctx, call_plan_sp, options, diagnostics);
 
                 // Check that the thread plan completed successfully
                 if (res != lldb::ExpressionResults::eExpressionCompleted)

source/Expression/LLVMUserExpression.cpp

 #include "lldb/Core/StreamFile.h"
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/ValueObjectConstResult.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/ExpressionSourceCode.h"
 #include "lldb/Expression/IRExecutionUnit.h"
 #include "lldb/Expression/IRInterpreter.h"

 #include "lldb/Host/HostInfo.h"
 #include "lldb/Symbol/Block.h"
 #include "lldb/Symbol/ClangASTContext.h"
+#include "lldb/Symbol/ClangExternalASTSourceCommon.h"
 #include "lldb/Symbol/Function.h"
 #include "lldb/Symbol/ObjectFile.h"
 #include "lldb/Symbol/SymbolVendor.h"
 #include "lldb/Symbol/Type.h"
-#include "lldb/Symbol/ClangExternalASTSourceCommon.h"
 #include "lldb/Symbol/VariableList.h"
 #include "lldb/Target/ExecutionContext.h"
 #include "lldb/Target/Process.h"

 }
 
 lldb::ExpressionResults
-LLVMUserExpression::Execute(Stream &error_stream, ExecutionContext &exe_ctx, const EvaluateExpressionOptions &options,
-                            lldb::UserExpressionSP &shared_ptr_to_me, lldb::ExpressionVariableSP &result)
+LLVMUserExpression::Execute(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+                            const EvaluateExpressionOptions &options, lldb::UserExpressionSP &shared_ptr_to_me,
+                            lldb::ExpressionVariableSP &result)
 {
     // The expression log is quite verbose, and if you're just tracking the execution of the
     // expression, it's quite convenient to have these logs come out with the STEP log as well.

     {
         lldb::addr_t struct_address = LLDB_INVALID_ADDRESS;
 
-        if (!PrepareToExecuteJITExpression(error_stream, exe_ctx, struct_address))
+        if (!PrepareToExecuteJITExpression(diagnostic_manager, exe_ctx, struct_address))
         {
-            error_stream.Printf("Errored out in %s, couldn't PrepareToExecuteJITExpression", __FUNCTION__);
+            diagnostic_manager.Printf(eDiagnosticSeverityError,
+                                      "errored out in %s, couldn't PrepareToExecuteJITExpression", __FUNCTION__);
             return lldb::eExpressionSetupError;
         }
 

 
             if (!module || !function)
             {
-                error_stream.Printf("Supposed to interpret, but nothing is there");
+                diagnostic_manager.PutCString(eDiagnosticSeverityError, "supposed to interpret, but nothing is there");
                 return lldb::eExpressionSetupError;
             }
 

 
             std::vector<lldb::addr_t> args;
 
-            if (!AddArguments(exe_ctx, args, struct_address, error_stream))
+            if (!AddArguments(exe_ctx, args, struct_address, diagnostic_manager))
             {
-                error_stream.Printf("Errored out in %s, couldn't AddArguments", __FUNCTION__);
+                diagnostic_manager.Printf(eDiagnosticSeverityError, "errored out in %s, couldn't AddArguments",
+                                          __FUNCTION__);
                 return lldb::eExpressionSetupError;
             }
 

 
             if (!interpreter_error.Success())
             {
-                error_stream.Printf("Supposed to interpret, but failed: %s", interpreter_error.AsCString());
+                diagnostic_manager.Printf(eDiagnosticSeverityError, "supposed to interpret, but failed: %s",
+                                          interpreter_error.AsCString());
                 return lldb::eExpressionDiscarded;
             }
         }

         {
             if (!exe_ctx.HasThreadScope())
             {
-                error_stream.Printf("UserExpression::Execute called with no thread selected.");
+                diagnostic_manager.Printf(eDiagnosticSeverityError, "%s called with no thread selected", __FUNCTION__);
                 return lldb::eExpressionSetupError;
             }
 

 
             std::vector<lldb::addr_t> args;
 
-            if (!AddArguments(exe_ctx, args, struct_address, error_stream))
+            if (!AddArguments(exe_ctx, args, struct_address, diagnostic_manager))
             {
-                error_stream.Printf("Errored out in %s, couldn't AddArguments", __FUNCTION__);
+                diagnostic_manager.Printf(eDiagnosticSeverityError, "errored out in %s, couldn't AddArguments",
+                                          __FUNCTION__);
                 return lldb::eExpressionSetupError;
             }
 
             lldb::ThreadPlanSP call_plan_sp(new ThreadPlanCallUserExpression(exe_ctx.GetThreadRef(), wrapper_address,
                                                                              args, options, shared_ptr_to_me));
 
-            if (!call_plan_sp || !call_plan_sp->ValidatePlan(&error_stream))
+            StreamString ss;
+            if (!call_plan_sp || !call_plan_sp->ValidatePlan(&ss))
+            {
+                diagnostic_manager.PutCString(eDiagnosticSeverityError, ss.GetData());
                 return lldb::eExpressionSetupError;
+            }
 
             ThreadPlanCallUserExpression *user_expression_plan =
                 static_cast<ThreadPlanCallUserExpression *>(call_plan_sp.get());

                 exe_ctx.GetProcessPtr()->SetRunningUserExpression(true);
 
             lldb::ExpressionResults execution_result =
-                exe_ctx.GetProcessRef().RunThreadPlan(exe_ctx, call_plan_sp, options, error_stream);
+                exe_ctx.GetProcessRef().RunThreadPlan(exe_ctx, call_plan_sp, options, diagnostic_manager);
 
             if (exe_ctx.GetProcessPtr())
                 exe_ctx.GetProcessPtr()->SetRunningUserExpression(false);

                         error_desc = real_stop_info_sp->GetDescription();
                 }
                 if (error_desc)
-                    error_stream.Printf("Execution was interrupted, reason: %s.", error_desc);
+                    diagnostic_manager.Printf(eDiagnosticSeverityError, "Execution was interrupted, reason: %s.",
+                                              error_desc);
                 else
-                    error_stream.PutCString("Execution was interrupted.");
+                    diagnostic_manager.PutCString(eDiagnosticSeverityError, "Execution was interrupted.");
 
                 if ((execution_result == lldb::eExpressionInterrupted && options.DoesUnwindOnError()) ||
                     (execution_result == lldb::eExpressionHitBreakpoint && options.DoesIgnoreBreakpoints()))
-                    error_stream.PutCString(
-                        "\nThe process has been returned to the state before expression evaluation.");
+                    diagnostic_manager.AppendMessageToDiagnostic(
+                        "The process has been returned to the state before expression evaluation.");
                 else
                 {
                     if (execution_result == lldb::eExpressionHitBreakpoint)
                         user_expression_plan->TransferExpressionOwnership();
-                    error_stream.PutCString(
-                        "\nThe process has been left at the point where it was interrupted, "
+                    diagnostic_manager.AppendMessageToDiagnostic(
+                        "The process has been left at the point where it was interrupted, "
                         "use \"thread return -x\" to return to the state before expression evaluation.");
                 }
 

             }
             else if (execution_result == lldb::eExpressionStoppedForDebug)
             {
-                error_stream.PutCString(
+                diagnostic_manager.PutCString(
+                    eDiagnosticSeverityRemark,
                     "Execution was halted at the first instruction of the expression "
                     "function because \"debug\" was requested.\n"
                     "Use \"thread return -x\" to return to the state before expression evaluation.");

             }
             else if (execution_result != lldb::eExpressionCompleted)
             {
-                error_stream.Printf("Couldn't execute function; result was %s\n",
+                diagnostic_manager.Printf(eDiagnosticSeverityError, "Couldn't execute function; result was %s",
                                           Process::ExecutionResultAsCString(execution_result));
                 return execution_result;
             }
         }
 
-        if (FinalizeJITExecution(error_stream, exe_ctx, result, function_stack_bottom, function_stack_top))
+        if (FinalizeJITExecution(diagnostic_manager, exe_ctx, result, function_stack_bottom, function_stack_top))
         {
             return lldb::eExpressionCompleted;
         }

     }
     else
     {
-        error_stream.Printf("Expression can't be run, because there is no JIT compiled function");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError,
+                                      "Expression can't be run, because there is no JIT compiled function");
         return lldb::eExpressionSetupError;
     }
 }
 
 bool
-LLVMUserExpression::FinalizeJITExecution(Stream &error_stream, ExecutionContext &exe_ctx,
+LLVMUserExpression::FinalizeJITExecution(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
                                          lldb::ExpressionVariableSP &result, lldb::addr_t function_stack_bottom,
                                          lldb::addr_t function_stack_top)
 {

 
     if (!m_dematerializer_sp)
     {
-        error_stream.Printf("Couldn't apply expression side effects : no dematerializer is present");
+        diagnostic_manager.Printf(eDiagnosticSeverityError,
+                                  "Couldn't apply expression side effects : no dematerializer is present");
         return false;
     }
 

 
     if (!dematerialize_error.Success())
     {
-        error_stream.Printf("Couldn't apply expression side effects : %s\n",
+        diagnostic_manager.Printf(eDiagnosticSeverityError, "Couldn't apply expression side effects : %s",
                                   dematerialize_error.AsCString("unknown error"));
         return false;
     }
 

 }
 
 bool
-LLVMUserExpression::PrepareToExecuteJITExpression(Stream &error_stream, ExecutionContext &exe_ctx,
+LLVMUserExpression::PrepareToExecuteJITExpression(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
                                                   lldb::addr_t &struct_address)
 {
     lldb::TargetSP target;

 
     if (!LockAndCheckContext(exe_ctx, target, process, frame))
     {
-        error_stream.Printf("The context has changed before we could JIT the expression!\n");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError,
+                                      "The context has changed before we could JIT the expression!");
         return false;
     }
 

 
             if (!alloc_error.Success())
             {
-                error_stream.Printf("Couldn't allocate space for materialized struct: %s\n", alloc_error.AsCString());
+                diagnostic_manager.Printf(eDiagnosticSeverityError,
+                                          "Couldn't allocate space for materialized struct: %s",
+                                          alloc_error.AsCString());
                 return false;
             }
         }

 
             if (!alloc_error.Success())
             {
-                error_stream.Printf("Couldn't allocate space for the stack frame: %s\n", alloc_error.AsCString());
+                diagnostic_manager.Printf(eDiagnosticSeverityError, "Couldn't allocate space for the stack frame: %s",
+                                          alloc_error.AsCString());
                 return false;
             }
         }

 
         if (!materialize_error.Success())
         {
-            error_stream.Printf("Couldn't materialize: %s\n", materialize_error.AsCString());
+            diagnostic_manager.Printf(eDiagnosticSeverityError, "Couldn't materialize: %s",
+                                      materialize_error.AsCString());
             return false;
         }
     }

source/Expression/UserExpression.cpp

 #include <string>
 #include <map>
 
+#include "Plugins/ExpressionParser/Clang/ClangPersistentVariables.h"
 #include "lldb/Core/ConstString.h"
 #include "lldb/Core/Log.h"
 #include "lldb/Core/Module.h"
 #include "lldb/Core/StreamFile.h"
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/ValueObjectConstResult.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/ExpressionSourceCode.h"
 #include "lldb/Expression/IRExecutionUnit.h"
 #include "lldb/Expression/IRInterpreter.h"
 #include "lldb/Expression/Materializer.h"
 #include "lldb/Expression/UserExpression.h"
-#include "Plugins/ExpressionParser/Clang/ClangPersistentVariables.h"
 #include "lldb/Host/HostInfo.h"
 #include "lldb/Symbol/Block.h"
 #include "lldb/Symbol/Function.h"

             log->Printf ("== [UserExpression::Evaluate] Getting expression: %s ==", error.AsCString());
         return lldb::eExpressionSetupError;
     }
- 
-    StreamString error_stream;
 
     if (log)
         log->Printf("== [UserExpression::Evaluate] Parsing expression %s ==", expr_cstr);

     if (options.InvokeCancelCallback (lldb::eExpressionEvaluationParse))
     {
         error.SetErrorString ("expression interrupted by callback before parse");
-        result_valobj_sp = ValueObjectConstResult::Create (exe_ctx.GetBestExecutionContextScope(), error);
+        result_valobj_sp = ValueObjectConstResult::Create(exe_ctx.GetBestExecutionContextScope(), error);
         return lldb::eExpressionInterrupted;
     }
 
-    if (!user_expression_sp->Parse (error_stream,
-                                    exe_ctx,
-                                    execution_policy,
-                                    keep_expression_in_memory,
-                                    generate_debug_info))
+    DiagnosticManager diagnostic_manager;
+
+    if (!user_expression_sp->Parse(diagnostic_manager, exe_ctx, execution_policy, keep_expression_in_memory,
+                                   generate_debug_info))
     {
         execution_results = lldb::eExpressionParseError;
-        if (error_stream.GetString().empty())
-            error.SetExpressionError (execution_results, "expression failed to parse, unknown error");
+        if (!diagnostic_manager.Diagnostics().size())
+            error.SetExpressionError(execution_results, "expression failed to parse, unknown error");
         else
-            error.SetExpressionError (execution_results, error_stream.GetString().c_str());
+            error.SetExpressionError(execution_results, diagnostic_manager.GetString().c_str());
     }
     else
     {

             if (log)
                 log->Printf("== [UserExpression::Evaluate] Expression may not run, but is not constant ==");
 
-            if (error_stream.GetString().empty())
-                error.SetExpressionError (lldb::eExpressionSetupError, "expression needed to run but couldn't");
+            if (!diagnostic_manager.Diagnostics().size())
+                error.SetExpressionError(lldb::eExpressionSetupError, "expression needed to run but couldn't");
         }
         else
         {

                 return lldb::eExpressionInterrupted;
             }
 
-            error_stream.GetString().clear();
+            diagnostic_manager.Clear();
 
             if (log)
                 log->Printf("== [UserExpression::Evaluate] Executing expression ==");
 
-            execution_results = user_expression_sp->Execute (error_stream,
-                                                             exe_ctx,
-                                                             options,
-                                                             user_expression_sp,
-                                                             expr_result);
+            execution_results =
+                user_expression_sp->Execute(diagnostic_manager, exe_ctx, options, user_expression_sp, expr_result);
 
             if (options.GetResultIsInternal() && expr_result && process)
             {

                 if (log)
                     log->Printf("== [UserExpression::Evaluate] Execution completed abnormally ==");
 
-                if (error_stream.GetString().empty())
-                    error.SetExpressionError (execution_results, "expression failed to execute, unknown error");
+                if (!diagnostic_manager.Diagnostics().size())
+                    error.SetExpressionError(execution_results, "expression failed to execute, unknown error");
                 else
-                    error.SetExpressionError (execution_results, error_stream.GetString().c_str());
+                    error.SetExpressionError(execution_results, diagnostic_manager.GetString().c_str());
             }
             else
             {

source/Expression/UtilityFunction.cpp

 #include "lldb/Core/Module.h"
 #include "lldb/Core/Stream.h"
 #include "lldb/Core/StreamFile.h"
+#include "lldb/Expression/DiagnosticManager.h"
+#include "lldb/Expression/ExpressionSourceCode.h"
 #include "lldb/Expression/FunctionCaller.h"
+#include "lldb/Expression/IRExecutionUnit.h"
 #include "lldb/Expression/UtilityFunction.h"
-#include "lldb/Expression/ExpressionSourceCode.h"
-#include "lldb/Expression/IRExecutionUnit.h"
 #include "lldb/Host/Host.h"
 #include "lldb/Target/ExecutionContext.h"
 #include "lldb/Target/Process.h"

     }
     if (m_caller_up)
     {
-        StreamString errors;
-        errors.Clear();
-        unsigned num_errors = m_caller_up->CompileFunction(errors);
+        DiagnosticManager diagnostics;
+
+        unsigned num_errors = m_caller_up->CompileFunction(diagnostics);
         if (num_errors)
         {
-            error.SetErrorStringWithFormat ("Error compiling %s caller function: \"%s\".",
-                                                m_function_name.c_str(),
-                                                errors.GetData());
+            error.SetErrorStringWithFormat("Error compiling %s caller function: \"%s\".", m_function_name.c_str(),
+                                           diagnostics.GetString().c_str());
             m_caller_up.reset();
             return nullptr;
         }
-        
-        errors.Clear();
+        diagnostics.Clear();
         ExecutionContext exe_ctx(process_sp);
-        
-        if (!m_caller_up->WriteFunctionWrapper(exe_ctx, errors))
+        if (!m_caller_up->WriteFunctionWrapper(exe_ctx, diagnostics))
         {
-            error.SetErrorStringWithFormat ("Error inserting caller function for %s: \"%s\".",
-                                                m_function_name.c_str(),
-                                                errors.GetData());
+            error.SetErrorStringWithFormat("Error inserting caller function for %s: \"%s\".", m_function_name.c_str(),
+                                           diagnostics.GetString().c_str());
             m_caller_up.reset();
             return nullptr;
         }

source/Plugins/ExpressionParser/Clang/ClangExpressionParser.h

 #ifndef liblldb_ClangExpressionParser_h_
 #define liblldb_ClangExpressionParser_h_
 
-#include "lldb/lldb-public.h"
 #include "lldb/Core/ArchSpec.h"
 #include "lldb/Core/ClangForward.h"
 #include "lldb/Core/Error.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/ExpressionParser.h"
+#include "lldb/lldb-public.h"
 
 #include <string>
 #include <vector>

     /// Parse a single expression and convert it to IR using Clang.  Don't
     /// wrap the expression in anything at all.
     ///
-    /// @param[in] stream
-    ///     The stream to print errors to.
+    /// @param[in] diagnostic_manager
+    ///     The diagnostic manager to report errors to.
     ///
     /// @return
     ///     The number of errors encountered during parsing.  0 means
     ///     success.
     //------------------------------------------------------------------
     unsigned
-    Parse (Stream &stream) override;
-    
+    Parse(DiagnosticManager &diagnostic_manager) override;
     //------------------------------------------------------------------
     /// Ready an already-parsed expression for execution, possibly
     /// evaluating it statically.

     ///
     /// @param[out] const_result
     ///     If the result of the expression is constant, and the
-    ///     expression has no side effects, this is set to the result of the 
+    ///     expression has no side effects, this is set to the result of the
     ///     expression.
     ///
     /// @param[in] execution_policy

source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp

 // C++ Includes
 // Other libraries and framework includes
 #include "clang/AST/ASTContext.h"
+#include "clang/AST/ASTDiagnostic.h"
 #include "clang/AST/ExternalASTSource.h"
+#include "clang/Basic/DiagnosticIDs.h"
 #include "clang/Basic/FileManager.h"
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Basic/TargetInfo.h"

 #include "lldb/Core/Module.h"
 #include "lldb/Core/Stream.h"
 #include "lldb/Core/StreamFile.h"
+#include "lldb/Core/StreamString.h"
 #include "lldb/Core/StringList.h"
-#include "lldb/Core/StreamString.h"
+#include "lldb/Expression/IRDynamicChecks.h"
 #include "lldb/Expression/IRExecutionUnit.h"
-#include "lldb/Expression/IRDynamicChecks.h"
 #include "lldb/Expression/IRInterpreter.h"
 #include "lldb/Host/File.h"
 #include "lldb/Host/HostInfo.h"
 #include "lldb/Symbol/ClangASTContext.h"
 #include "lldb/Symbol/SymbolVendor.h"
 #include "lldb/Target/ExecutionContext.h"
+#include "lldb/Target/Language.h"
 #include "lldb/Target/ObjCLanguageRuntime.h"
 #include "lldb/Target/Process.h"
 #include "lldb/Target/Target.h"
-#include "lldb/Target/Language.h"
+#include "lldb/Utility/LLDBAssert.h"
 
 using namespace clang;
 using namespace llvm;

     }
 };
 
+class ClangDiagnosticManagerAdapter : public clang::DiagnosticConsumer
+{
+public:
+    ClangDiagnosticManagerAdapter() : m_passthrough(new clang::TextDiagnosticBuffer) {}
+
+    ClangDiagnosticManagerAdapter(const std::shared_ptr<clang::TextDiagnosticBuffer> &passthrough)
+        : m_passthrough(passthrough)
+    {
+    }
+
+    void
+    ResetManager(DiagnosticManager *manager = nullptr)
+    {
+        m_manager = manager;
+    }
+
+    void
+    HandleDiagnostic(DiagnosticsEngine::Level DiagLevel, const clang::Diagnostic &Info)
+    {
+        if (m_manager)
+        {
+            llvm::SmallVector<char, 32> diag_str;
+            Info.FormatDiagnostic(diag_str);
+            diag_str.push_back('\0');
+            const char *data = diag_str.data();
+
+            switch (DiagLevel)
+            {
+                case DiagnosticsEngine::Level::Fatal:
+                case DiagnosticsEngine::Level::Error:
+                    m_manager->AddDiagnostic(data, eDiagnosticSeverityError, eDiagnosticOriginClang, Info.getID());
+                    break;
+                case DiagnosticsEngine::Level::Warning:
+                    m_manager->AddDiagnostic(data, eDiagnosticSeverityWarning, eDiagnosticOriginClang, Info.getID());
+                    break;
+                case DiagnosticsEngine::Level::Remark:
+                case DiagnosticsEngine::Level::Ignored:
+                    m_manager->AddDiagnostic(data, eDiagnosticSeverityRemark, eDiagnosticOriginClang, Info.getID());
+                    break;
+                case DiagnosticsEngine::Level::Note:
+                    m_manager->AppendMessageToDiagnostic(data);
+            }
+        }
+
+        m_passthrough->HandleDiagnostic(DiagLevel, Info);
+    }
+
+    void
+    FlushDiagnostics(DiagnosticsEngine &Diags)
+    {
+        m_passthrough->FlushDiagnostics(Diags);
+    }
+
+    DiagnosticConsumer *
+    clone(DiagnosticsEngine &Diags) const
+    {
+        return new ClangDiagnosticManagerAdapter(m_passthrough);
+    }
+
+    clang::TextDiagnosticBuffer *
+    GetPassthrough()
+    {
+        return m_passthrough.get();
+    }
+
+private:
+    DiagnosticManager *m_manager = nullptr;
+    std::shared_ptr<clang::TextDiagnosticBuffer> m_passthrough;
+};
+
 //===----------------------------------------------------------------------===//
 // Implementation of ClangExpressionParser
 //===----------------------------------------------------------------------===//

 
     // 6. Set up the diagnostic buffer for reporting errors
 
-    m_compiler->getDiagnostics().setClient(new clang::TextDiagnosticBuffer);
+    m_compiler->getDiagnostics().setClient(new ClangDiagnosticManagerAdapter);
 
     // 7. Set up the source management objects inside the compiler
 

 }
 
 unsigned
-ClangExpressionParser::Parse(Stream &stream)
+ClangExpressionParser::Parse(DiagnosticManager &diagnostic_manager)
 {
-    TextDiagnosticBuffer *diag_buf = static_cast<TextDiagnosticBuffer *>(m_compiler->getDiagnostics().getClient());
+    ClangDiagnosticManagerAdapter *adapter =
+        static_cast<ClangDiagnosticManagerAdapter *>(m_compiler->getDiagnostics().getClient());
+    clang::TextDiagnosticBuffer *diag_buf = adapter->GetPassthrough();
     diag_buf->FlushDiagnostics(m_compiler->getDiagnostics());
 
+    adapter->ResetManager(&diagnostic_manager);
+
     const char *expr_text = m_expr.Text();
 
     clang::SourceManager &source_mgr = m_compiler->getSourceManager();

     if (m_pp_callbacks && m_pp_callbacks->hasErrors())
     {
         num_errors++;
-        stream.PutCString(m_pp_callbacks->getErrorString().c_str());
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "while importing modules:");
+        diagnostic_manager.AppendMessageToDiagnostic(m_pp_callbacks->getErrorString().c_str());
     }
 
-    for (TextDiagnosticBuffer::const_iterator warn = diag_buf->warn_begin(), warn_end = diag_buf->warn_end();
-         warn != warn_end; ++warn)
-        stream.Printf("warning: %s\n", warn->second.c_str());
-
-    for (TextDiagnosticBuffer::const_iterator err = diag_buf->err_begin(), err_end = diag_buf->err_end();
-         err != err_end; ++err)
-        stream.Printf("error: %s\n", err->second.c_str());
-
-    for (TextDiagnosticBuffer::const_iterator note = diag_buf->note_begin(), note_end = diag_buf->note_end();
-         note != note_end; ++note)
-        stream.Printf("note: %s\n", note->second.c_str());
-
     if (!num_errors)
     {
         if (type_system_helper->DeclMap() && !type_system_helper->DeclMap()->ResolveUnknownTypes())
         {
-            stream.Printf("error: Couldn't infer the type of a variable\n");
+            diagnostic_manager.Printf(eDiagnosticSeverityError, "Couldn't infer the type of a variable");
             num_errors++;
         }
     }
 
+    adapter->ResetManager();
+
     return num_errors;
 }
 

                 {
                     DynamicCheckerFunctions *dynamic_checkers = new DynamicCheckerFunctions();
 
-                    StreamString install_errors;
+                    DiagnosticManager install_diagnostics;
 
-                    if (!dynamic_checkers->Install(install_errors, exe_ctx))
+                    if (!dynamic_checkers->Install(install_diagnostics, exe_ctx))
                     {
-                        if (install_errors.GetString().empty())
-                            err.SetErrorString ("couldn't install checkers, unknown error");
+                        if (install_diagnostics.Diagnostics().size())
+                            err.SetErrorString("couldn't install checkers, unknown error");
                         else
-                            err.SetErrorString (install_errors.GetString().c_str());
+                            err.SetErrorString(install_diagnostics.GetString().c_str());
 
                         return err;
                     }

source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.h

     //------------------------------------------------------------------
     /// Compile the wrapper function
     ///
-    /// @param[in] errors
-    ///     The stream to print parser errors to.
+    /// @param[in] diagnostic_manager
+    ///     The diagnostic manager to report parser errors to.
     ///
     /// @return
     ///     The number of errors.
     //------------------------------------------------------------------
     unsigned
-    CompileFunction (Stream &errors) override;
-    
+    CompileFunction(DiagnosticManager &diagnostic_manager) override;
     ExpressionTypeSystemHelper *
-    GetTypeSystemHelper () override
+    GetTypeSystemHelper() override
     {
         return &m_type_system_helper;
     }

source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.cpp

 }
 
 unsigned
-ClangFunctionCaller::CompileFunction (Stream &errors)
+ClangFunctionCaller::CompileFunction(DiagnosticManager &diagnostic_manager)
 {
     if (m_compiled)
         return 0;
-    
     // FIXME: How does clang tell us there's no return value?  We need to handle that case.
     unsigned num_errors = 0;
     

                 type_name = clang_qual_type.GetTypeName().AsCString("");
             }
             else
-            {   
-                errors.Printf("Could not determine type of input value %" PRIu64 ".", (uint64_t)i);
+            {
+                diagnostic_manager.Printf(eDiagnosticSeverityError,
+                                          "Could not determine type of input value %" PRIu64 ".", (uint64_t)i);
                 return 1;
             }
         }

     {
         const bool generate_debug_info = true;
         m_parser.reset(new ClangExpressionParser(jit_process_sp.get(), *this, generate_debug_info));
-        
-        num_errors = m_parser->Parse (errors);
+        num_errors = m_parser->Parse(diagnostic_manager);
     }
     else
     {
-        errors.Printf("no process - unable to inject function");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "no process - unable to inject function");
         num_errors = 1;
     }
-    
     m_compiled = (num_errors == 0);
     
     if (!m_compiled)

source/Plugins/ExpressionParser/Clang/ClangUserExpression.h

     //------------------------------------------------------------------
     /// Parse the expression
     ///
-    /// @param[in] error_stream
-    ///     A stream to print parse errors and warnings to.
+    /// @param[in] diagnostic_manager
+    ///     A diagnostic manager to report parse errors and warnings to.
     ///
     /// @param[in] exe_ctx
     ///     The execution context to use when looking up entities that

     ///     True on success (no errors); false otherwise.
     //------------------------------------------------------------------
     bool
-    Parse (Stream &error_stream,
-           ExecutionContext &exe_ctx,
-           lldb_private::ExecutionPolicy execution_policy,
-           bool keep_result_in_memory,
-           bool generate_debug_info) override;
+    Parse(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+          lldb_private::ExecutionPolicy execution_policy, bool keep_result_in_memory,
+          bool generate_debug_info) override;
 
     ExpressionTypeSystemHelper *
     GetTypeSystemHelper () override

                  lldb_private::Error &err) override;
 
     bool
-    AddArguments (ExecutionContext &exe_ctx,
-                  std::vector<lldb::addr_t> &args,
-                  lldb::addr_t struct_address,
-                  Stream &error_stream) override;
-    
-    ClangUserExpressionHelper   m_type_system_helper;
-    
+    AddArguments(ExecutionContext &exe_ctx, std::vector<lldb::addr_t> &args, lldb::addr_t struct_address,
+                 DiagnosticManager &diagnostic_manager) override;
+
+    ClangUserExpressionHelper m_type_system_helper;
     class ResultDelegate : public Materializer::PersistentVariableDelegate
     {
     public:

source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp

 }
 
 bool
-ClangUserExpression::Parse (Stream &error_stream,
-                            ExecutionContext &exe_ctx,
-                            lldb_private::ExecutionPolicy execution_policy,
-                            bool keep_result_in_memory,
-                            bool generate_debug_info)
+ClangUserExpression::Parse(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+                           lldb_private::ExecutionPolicy execution_policy, bool keep_result_in_memory,
+                           bool generate_debug_info)
 {
     Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS));
 

         }
         else
         {
-            error_stream.PutCString ("error: couldn't start parsing (no persistent data)");
+            diagnostic_manager.PutCString(eDiagnosticSeverityError, "couldn't start parsing (no persistent data)");
             return false;
         }
     }
     else
     {
-        error_stream.PutCString ("error: couldn't start parsing (no target)");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "error: couldn't start parsing (no target)");
         return false;
     }
 

 
     if (!err.Success())
     {
-        error_stream.Printf("warning: %s\n", err.AsCString());
+        diagnostic_manager.PutCString(eDiagnosticSeverityWarning, err.AsCString());
     }
 
     StreamString m_transformed_stream;

 
     if (!source_code->GetText(m_transformed_text, lang_type, m_const_object, m_in_static_method, exe_ctx))
     {
-        error_stream.PutCString ("error: couldn't construct expression body");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "couldn't construct expression body");
         return false;
     }
 

 
     if (!target)
     {
-        error_stream.PutCString ("error: invalid target\n");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "invalid target");
         return false;
     }
 

 
     if (!DeclMap()->WillParse(exe_ctx, m_materializer_ap.get()))
     {
-        error_stream.PutCString ("error: current process state is unsuitable for expression parsing\n");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError,
+                                      "current process state is unsuitable for expression parsing");
 
         ResetDeclMap(); // We are being careful here in the case of breakpoint conditions.
 

 
     ClangExpressionParser parser(exe_scope, *this, generate_debug_info);
 
-    unsigned num_errors = parser.Parse (error_stream);
+    unsigned num_errors = parser.Parse(diagnostic_manager);
 
     if (num_errors)
     {
-        error_stream.Printf ("error: %d errors parsing expression\n", num_errors);
+        diagnostic_manager.Printf(eDiagnosticSeverityError, "%u error%s parsing expression", num_errors,
+                                  num_errors == 1 ? "" : "s");
 
         ResetDeclMap(); // We are being careful here in the case of breakpoint conditions.
 

     {
         const char *error_cstr = jit_error.AsCString();
         if (error_cstr && error_cstr[0])
-            error_stream.Printf ("error: %s\n", error_cstr);
+            diagnostic_manager.PutCString(eDiagnosticSeverityError, error_cstr);
         else
-            error_stream.Printf ("error: expression can't be interpreted or run\n");
+            diagnostic_manager.Printf(eDiagnosticSeverityError, "expression can't be interpreted or run");
         return false;
     }
 }
 
 bool
-ClangUserExpression::AddArguments (ExecutionContext &exe_ctx,
-                                   std::vector<lldb::addr_t> &args,
-                                   lldb::addr_t struct_address,
-                                   Stream &error_stream)
+ClangUserExpression::AddArguments(ExecutionContext &exe_ctx, std::vector<lldb::addr_t> &args,
+                                  lldb::addr_t struct_address, DiagnosticManager &diagnostic_manager)
 {
     lldb::addr_t object_ptr = LLDB_INVALID_ADDRESS;
-    lldb::addr_t cmd_ptr    = LLDB_INVALID_ADDRESS;
-    
+    lldb::addr_t cmd_ptr = LLDB_INVALID_ADDRESS;
     if (m_needs_object_ptr)
     {
         lldb::StackFrameSP frame_sp = exe_ctx.GetFrameSP();

         }
         else
         {
-            error_stream.Printf("Need object pointer but don't know the language\n");
+            diagnostic_manager.PutCString(eDiagnosticSeverityError, "need object pointer but don't know the language");
             return false;
         }
 

 
         if (!object_ptr_error.Success())
         {
-            error_stream.Printf("warning: couldn't get required object pointer (substituting NULL): %s\n", object_ptr_error.AsCString());
+            diagnostic_manager.Printf(eDiagnosticSeverityWarning,
+                                      "couldn't get required object pointer (substituting NULL): %s",
+                                      object_ptr_error.AsCString());
             object_ptr = 0;
         }
 

 
             if (!object_ptr_error.Success())
             {
-                error_stream.Printf("warning: couldn't get cmd pointer (substituting NULL): %s\n", object_ptr_error.AsCString());
+                diagnostic_manager.Printf(eDiagnosticSeverityWarning,
+                                          "couldn't get cmd pointer (substituting NULL): %s",
+                                          object_ptr_error.AsCString());
                 cmd_ptr = 0;
             }
         }

source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.h

     {
         m_type_system_helper.ResetDeclMap(exe_ctx, keep_result_in_memory);
     }
-    
     bool
-    Install (Stream &error_stream, ExecutionContext &exe_ctx) override;
-    
+    Install(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx) override;
 private:
-    ClangUtilityFunctionHelper  m_type_system_helper;    ///< The map to use when parsing and materializing the expression.
+    ClangUtilityFunctionHelper m_type_system_helper; ///< The map to use when parsing and materializing the expression.
 };
 
 } // namespace lldb_private

source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.cpp

 //------------------------------------------------------------------
 /// Install the utility function into a process
 ///
-/// @param[in] error_stream
-///     A stream to print parse errors and warnings to.
+/// @param[in] diagnostic_manager
+///     A diagnostic manager to report errors and warnings to.
 ///
 /// @param[in] exe_ctx
 ///     The execution context to install the utility function to.

 ///     True on success (no errors); false otherwise.
 //------------------------------------------------------------------
 bool
-ClangUtilityFunction::Install (Stream &error_stream,
-                               ExecutionContext &exe_ctx)
+ClangUtilityFunction::Install(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx)
 {
     if (m_jit_start_addr != LLDB_INVALID_ADDRESS)
     {
-        error_stream.PutCString("error: already installed\n");
+        diagnostic_manager.PutCString(eDiagnosticSeverityWarning, "already installed");
         return false;
     }
-    
     ////////////////////////////////////
     // Set up the target and compiler
     //
     
     Target *target = exe_ctx.GetTargetPtr();
-    
     if (!target)
     {
-        error_stream.PutCString ("error: invalid target\n");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "invalid target");
         return false;
     }
-    
     Process *process = exe_ctx.GetProcessPtr();
-    
     if (!process)
     {
-        error_stream.PutCString ("error: invalid process\n");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "invalid process");
         return false;
     }
-        
     //////////////////////////
     // Parse the expression
     //

     bool keep_result_in_memory = false;
     
     ResetDeclMap(exe_ctx, keep_result_in_memory);
-    
     if (!DeclMap()->WillParse(exe_ctx, NULL))
     {
-        error_stream.PutCString ("error: current process state is unsuitable for expression parsing\n");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError,
+                                      "current process state is unsuitable for expression parsing");
         return false;
     }
-    
     const bool generate_debug_info = true;
     ClangExpressionParser parser(exe_ctx.GetBestExecutionContextScope(), *this, generate_debug_info);
-    
-    unsigned num_errors = parser.Parse (error_stream);
-    
+    unsigned num_errors = parser.Parse(diagnostic_manager);
     if (num_errors)
     {
-        error_stream.Printf ("error: %d errors parsing expression\n", num_errors);
-        
+        diagnostic_manager.Printf(eDiagnosticSeverityError, "%d error%s parsing expression", num_errors,
+                                  num_errors == 1 ? "" : "s");
+
         ResetDeclMap();
-        
         return false;
     }
     

     {
         const char *error_cstr = jit_error.AsCString();
         if (error_cstr && error_cstr[0])
-            error_stream.Printf ("error: %s\n", error_cstr);
+        {
+            diagnostic_manager.Printf(eDiagnosticSeverityError, "%s", error_cstr);
+        }
         else
-            error_stream.Printf ("error: expression can't be interpreted or run\n");
+        {
+            diagnostic_manager.PutCString(eDiagnosticSeverityError, "expression can't be interpreted or run");
+        }
         return false;
     }
 }

source/Plugins/ExpressionParser/Go/GoUserExpression.h

 class GoUserExpression : public UserExpression
 {
   public:
       GoUserExpression(ExecutionContextScope &exe_scope, const char *expr, const char *expr_prefix,
                        lldb::LanguageType language, ResultType desired_type, const EvaluateExpressionOptions &options);
 
       bool
-    Parse(Stream &error_stream, ExecutionContext &exe_ctx, lldb_private::ExecutionPolicy execution_policy,
-          bool keep_result_in_memory, bool generate_debug_info) override;
+      Parse(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+            lldb_private::ExecutionPolicy execution_policy, bool keep_result_in_memory,
+            bool generate_debug_info) override;
 
       lldb::ExpressionResults
-    Execute(Stream &error_stream, ExecutionContext &exe_ctx,
-            const EvaluateExpressionOptions &options,
-            lldb::UserExpressionSP &shared_ptr_to_me,
-            lldb::ExpressionVariableSP &result) override;
+      Execute(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+              const EvaluateExpressionOptions &options, lldb::UserExpressionSP &shared_ptr_to_me,
+              lldb::ExpressionVariableSP &result) override;
 
       bool
       CanInterpret() override
       {
           return true;
+      }
+      bool
+      FinalizeJITExecution(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+                           lldb::ExpressionVariableSP &result,
+                           lldb::addr_t function_stack_bottom = LLDB_INVALID_ADDRESS,
+                           lldb::addr_t function_stack_top = LLDB_INVALID_ADDRESS) override
+      {
+          return true;
     }
-    bool
-    FinalizeJITExecution(Stream &error_stream, ExecutionContext &exe_ctx, lldb::ExpressionVariableSP &result,
-                         lldb::addr_t function_stack_bottom = LLDB_INVALID_ADDRESS,
-                         lldb::addr_t function_stack_top = LLDB_INVALID_ADDRESS) override
-    {
-        return true;
-    }
 
   private:
     class GoInterpreter;

source/Plugins/ExpressionParser/Go/GoUserExpression.cpp

 // Project includes
 #include "GoUserExpression.h"
 
-#include "lldb/lldb-private.h"
 #include "lldb/Core/ConstString.h"
 #include "lldb/Core/DataBufferHeap.h"
 #include "lldb/Core/DataEncoder.h"

 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/ValueObjectConstResult.h"
 #include "lldb/Core/ValueObjectRegister.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/ExpressionVariable.h"
-#include "lldb/Symbol/TypeList.h"
 #include "lldb/Symbol/GoASTContext.h"
 #include "lldb/Symbol/SymbolFile.h"
+#include "lldb/Symbol/TypeList.h"
 #include "lldb/Symbol/VariableList.h"
 #include "lldb/Target/ExecutionContext.h"
 #include "lldb/Target/Process.h"

 #include "lldb/Target/Target.h"
 #include "lldb/Target/ThreadPlan.h"
 #include "lldb/Target/ThreadPlanCallUserExpression.h"
+#include "lldb/lldb-private.h"
 
 #include "Plugins/ExpressionParser/Go/GoAST.h"
 #include "Plugins/ExpressionParser/Go/GoParser.h"

 }
 
 bool
-GoUserExpression::Parse(Stream &error_stream, ExecutionContext &exe_ctx, lldb_private::ExecutionPolicy execution_policy,
-                        bool keep_result_in_memory, bool generate_debug_info)
+GoUserExpression::Parse(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+                        lldb_private::ExecutionPolicy execution_policy, bool keep_result_in_memory,
+                        bool generate_debug_info)
 {
     InstallContext(exe_ctx);
     m_interpreter.reset(new GoInterpreter(exe_ctx, GetUserText()));

         return true;
     const char *error_cstr = m_interpreter->error().AsCString();
     if (error_cstr && error_cstr[0])
-        error_stream.Printf("error: %s\n", error_cstr);
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, error_cstr);
     else
-        error_stream.Printf("error: expression can't be interpreted or run\n");
+        diagnostic_manager.Printf(eDiagnosticSeverityError, "expression can't be interpreted or run");
     return false;
 }
 
 lldb::ExpressionResults
-GoUserExpression::Execute(Stream &error_stream, ExecutionContext &exe_ctx, const EvaluateExpressionOptions &options,
-                          lldb::UserExpressionSP &shared_ptr_to_me, lldb::ExpressionVariableSP &result)
+GoUserExpression::Execute(DiagnosticManager &diagnostic_manager, ExecutionContext &exe_ctx,
+                          const EvaluateExpressionOptions &options, lldb::UserExpressionSP &shared_ptr_to_me,
+                          lldb::ExpressionVariableSP &result)
 {
     Log *log(lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_EXPRESSIONS | LIBLLDB_LOG_STEP));
 

             if (log)
                 log->Printf("== [GoUserExpression::Evaluate] Expression may not run, but is not constant ==");
 
-            error_stream.Printf("expression needed to run but couldn't");
+            diagnostic_manager.PutCString(eDiagnosticSeverityError, "expression needed to run but couldn't");
 
             return execution_results;
         }

     {
         const char *error_cstr = err.AsCString();
         if (error_cstr && error_cstr[0])
-            error_stream.Printf("error: %s\n", error_cstr);
+            diagnostic_manager.PutCString(eDiagnosticSeverityError, error_cstr);
         else
-            error_stream.Printf("error: expression can't be interpreted or run\n");
+            diagnostic_manager.PutCString(eDiagnosticSeverityError, "expression can't be interpreted or run");
         return lldb::eExpressionDiscarded;
     }
     result.reset(new ExpressionVariable(ExpressionVariable::eKindGo));

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

 #include "lldb/Core/Section.h"
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/ValueObject.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/FunctionCaller.h"
 #include "lldb/Symbol/ClangASTContext.h"
 #include "lldb/Symbol/ObjectFile.h"

             exe_ctx.SetFrameSP(thread->GetSelectedFrame());
         }
     }
-    
     // Now we're ready to call the function:
-    
-    StreamString error_stream;
+    DiagnosticManager diagnostics;
     lldb::addr_t wrapper_struct_addr = LLDB_INVALID_ADDRESS;
 
     if (!m_print_object_caller_up)

             strm.Printf("Could not get function runner to call print for debugger function: %s.", error.AsCString());
             return false;
         }
-        m_print_object_caller_up->InsertFunction(exe_ctx, wrapper_struct_addr, error_stream);
+        m_print_object_caller_up->InsertFunction(exe_ctx, wrapper_struct_addr, diagnostics);
     }
     else
     {
-        m_print_object_caller_up->WriteFunctionArguments(exe_ctx,
-                                                         wrapper_struct_addr,
-                                                         arg_value_list,
-                                                         error_stream);
+        m_print_object_caller_up->WriteFunctionArguments(exe_ctx, wrapper_struct_addr, arg_value_list, diagnostics);
     }
 
-    
-
     EvaluateExpressionOptions options;
     options.SetUnwindOnError(true);
     options.SetTryAllThreads(true);
     options.SetStopOthers(true);
     options.SetIgnoreBreakpoints(true);
     options.SetTimeoutUsec(PO_FUNCTION_TIMEOUT_USEC);
-    
-    ExpressionResults results = m_print_object_caller_up->ExecuteFunction (exe_ctx,
-                                                                           &wrapper_struct_addr,
-                                                                           options,
-                                                                           error_stream,
-                                                                           ret);
+    ExpressionResults results =
+        m_print_object_caller_up->ExecuteFunction(exe_ctx, &wrapper_struct_addr, options, diagnostics, ret);
     if (results != eExpressionCompleted)
     {
         strm.Printf("Error evaluating Print Object function: %d.\n", results);

source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntimeV2.cpp

 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/Timer.h"
 #include "lldb/Core/ValueObjectVariable.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/FunctionCaller.h"
 #include "lldb/Expression/UtilityFunction.h"
 #include "lldb/Host/StringConvert.h"

     
     if (!ast)
         return false;
-    
     Address function_address;
-    
-    StreamString errors;
-    
+    DiagnosticManager diagnostics;
     const uint32_t addr_size = process->GetAddressByteSize();
-    
     Error err;
     
     // Read the total number of classes from the hash table

         }
         else
         {
-            errors.Clear();
-            
-            if (!m_get_class_info_code->Install(errors, exe_ctx))
+            diagnostics.Clear();
+            if (!m_get_class_info_code->Install(diagnostics, exe_ctx))
             {
                 if (log)
-                    log->Printf ("Failed to install implementation lookup: %s.", errors.GetData());
+                {
+                    log->Printf("Failed to install implementation lookup");
+                    diagnostics.Dump(log);
+                }
                 m_get_class_info_code.reset();
             }
         }

         if (!get_class_info_function)
         {
             if (log)
-                log->Printf ("Failed to get implementation lookup function caller: %s.", errors.GetData());
+            {
+                log->Printf("Failed to get implementation lookup function caller.");
+                diagnostics.Dump(log);
+            }
+
             return false;
         }
         arguments = get_class_info_function->GetArgumentValues();
     }
 
-    errors.Clear();
-    
+    diagnostics.Clear();
     const uint32_t class_info_byte_size = addr_size + 4;
     const uint32_t class_infos_byte_size = num_classes * class_info_byte_size;
     lldb::addr_t class_infos_addr = process->AllocateMemory(class_infos_byte_size,

     arguments.GetValueAtIndex(0)->GetScalar() = hash_table.GetTableLoadAddress();
     arguments.GetValueAtIndex(1)->GetScalar() = class_infos_addr;
     arguments.GetValueAtIndex(2)->GetScalar() = class_infos_byte_size;
-    
     bool success = false;
-    
-    errors.Clear();
-    
+    diagnostics.Clear();
     // Write our function arguments into the process so we can run our function
-    if (get_class_info_function->WriteFunctionArguments (exe_ctx,
-                                                           m_get_class_info_args,
-                                                           arguments,
-                                                           errors))
+    if (get_class_info_function->WriteFunctionArguments(exe_ctx, m_get_class_info_args, arguments, diagnostics))
     {
         EvaluateExpressionOptions options;
         options.SetUnwindOnError(true);

         Value return_value;
         return_value.SetValueType (Value::eValueTypeScalar);
         //return_value.SetContext (Value::eContextTypeClangType, clang_uint32_t_type);
-        return_value.SetCompilerType (clang_uint32_t_type);
+        return_value.SetCompilerType(clang_uint32_t_type);
         return_value.GetScalar() = 0;
-        
-        errors.Clear();
-        
+        diagnostics.Clear();
         // Run the function
-        ExpressionResults results = get_class_info_function->ExecuteFunction (exe_ctx,
-                                                                              &m_get_class_info_args,
-                                                                              options,
-                                                                              errors,
-                                                                              return_value);
-        
+        ExpressionResults results = get_class_info_function->ExecuteFunction(exe_ctx, &m_get_class_info_args, options,
+                                                                             diagnostics, return_value);
+
         if (results == eExpressionCompleted)
         {
             // The result is the number of ClassInfo structures that were filled in

         else
         {
             if (log)
-                log->Printf("Error evaluating our find class name function: %s.\n", errors.GetData());
+            {
+                log->Printf("Error evaluating our find class name function.");
+                diagnostics.Dump(log);
+            }
         }
     }
     else
     {
         if (log)
-            log->Printf ("Error writing function arguments: \"%s\".", errors.GetData());
+        {
+            log->Printf("Error writing function arguments.");
+            diagnostics.Dump(log);
+        }
     }
-    
     // Deallocate the memory we allocated for the ClassInfo array
     process->DeallocateMemory(class_infos_addr);
     

     
     if (!ast)
         return DescriptorMapUpdateResult::Fail();
-    
     Address function_address;
-    
-    StreamString errors;
-    
+    DiagnosticManager diagnostics;
     const uint32_t addr_size = process->GetAddressByteSize();
-    
     Error err;
     
     const lldb::addr_t objc_opt_ptr = GetSharedCacheReadOnlyAddress();

         }
         else
         {
-            errors.Clear();
-            
-            if (!m_get_shared_cache_class_info_code->Install(errors, exe_ctx))
+            diagnostics.Clear();
+            if (!m_get_shared_cache_class_info_code->Install(diagnostics, exe_ctx))
             {
                 if (log)
-                    log->Printf ("Failed to install implementation lookup: %s.", errors.GetData());
+                {
+                    log->Printf("Failed to install implementation lookup.");
+                    diagnostics.Dump(log);
+                }
                 m_get_shared_cache_class_info_code.reset();
             }
         }
-        
         if (!m_get_shared_cache_class_info_code.get())
             return DescriptorMapUpdateResult::Fail();
     

             return DescriptorMapUpdateResult::Fail();
         arguments = get_shared_cache_class_info_function->GetArgumentValues();
     }
-    
-    errors.Clear();
-    
+    diagnostics.Clear();
     const uint32_t class_info_byte_size = addr_size + 4;
     const uint32_t class_infos_byte_size = num_classes * class_info_byte_size;
     lldb::addr_t class_infos_addr = process->AllocateMemory (class_infos_byte_size,

     arguments.GetValueAtIndex(0)->GetScalar() = objc_opt_ptr;
     arguments.GetValueAtIndex(1)->GetScalar() = class_infos_addr;
     arguments.GetValueAtIndex(2)->GetScalar() = class_infos_byte_size;
-    
     bool success = false;
     bool any_found = false;
-    
-    errors.Clear();
-    
+    diagnostics.Clear();
     // Write our function arguments into the process so we can run our function
-    if (get_shared_cache_class_info_function->WriteFunctionArguments (exe_ctx,
-                                                                      m_get_shared_cache_class_info_args,
-                                                                      arguments,
-                                                                      errors))
+    if (get_shared_cache_class_info_function->WriteFunctionArguments(exe_ctx, m_get_shared_cache_class_info_args,
+                                                                     arguments, diagnostics))
     {
         EvaluateExpressionOptions options;
         options.SetUnwindOnError(true);

         Value return_value;
         return_value.SetValueType (Value::eValueTypeScalar);
         //return_value.SetContext (Value::eContextTypeClangType, clang_uint32_t_type);
-        return_value.SetCompilerType (clang_uint32_t_type);
+        return_value.SetCompilerType(clang_uint32_t_type);
         return_value.GetScalar() = 0;
-        
-        errors.Clear();
-        
+        diagnostics.Clear();
         // Run the function
-        ExpressionResults results = get_shared_cache_class_info_function->ExecuteFunction (exe_ctx,
-                                                                                           &m_get_shared_cache_class_info_args,
-                                                                                           options,
-                                                                                           errors,
-                                                                                           return_value);
-        
+        ExpressionResults results = get_shared_cache_class_info_function->ExecuteFunction(
+            exe_ctx, &m_get_shared_cache_class_info_args, options, diagnostics, return_value);
+
         if (results == eExpressionCompleted)
         {
             // The result is the number of ClassInfo structures that were filled in

         else
         {
             if (log)
-                log->Printf("Error evaluating our find class name function: %s.\n", errors.GetData());
+            {
+                log->Printf("Error evaluating our find class name function.");
+                diagnostics.Dump(log);
+            }
         }
     }
     else
     {
         if (log)
-            log->Printf ("Error writing function arguments: \"%s\".", errors.GetData());
+        {
+            log->Printf("Error writing function arguments.");
+            diagnostics.Dump(log);
+        }
     }
-    
     // Deallocate the memory we allocated for the ClassInfo array
     process->DeallocateMemory(class_infos_addr);
     

source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCTrampolineHandler.cpp

 #include "lldb/Core/Module.h"
 #include "lldb/Core/StreamFile.h"
 #include "lldb/Core/Value.h"
+#include "lldb/Expression/DiagnosticManager.h"
+#include "lldb/Expression/FunctionCaller.h"
 #include "lldb/Expression/UserExpression.h"
-#include "lldb/Expression/FunctionCaller.h"
 #include "lldb/Expression/UtilityFunction.h"
 #include "lldb/Host/FileSpec.h"
 #include "lldb/Symbol/ClangASTContext.h"
 #include "lldb/Symbol/Symbol.h"
 #include "lldb/Target/ABI.h"
+#include "lldb/Target/ExecutionContext.h"
 #include "lldb/Target/ObjCLanguageRuntime.h"
 #include "lldb/Target/Process.h"
 #include "lldb/Target/RegisterContext.h"
 #include "lldb/Target/Target.h"
 #include "lldb/Target/Thread.h"
-#include "lldb/Target/ExecutionContext.h"
 #include "lldb/Target/ThreadPlanRunToAddress.h"
 
 #include "llvm/ADT/STLExtras.h"

 }
 
 lldb::addr_t
-AppleObjCTrampolineHandler::SetupDispatchFunction (Thread &thread, ValueList &dispatch_values)
+AppleObjCTrampolineHandler::SetupDispatchFunction(Thread &thread, ValueList &dispatch_values)
 {
-    ExecutionContext exe_ctx (thread.shared_from_this());
-    StreamString errors;
-    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_STEP));
+    ExecutionContext exe_ctx(thread.shared_from_this());
+    DiagnosticManager diagnostics;
+    Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_STEP));
     lldb::addr_t args_addr = LLDB_INVALID_ADDRESS;
     FunctionCaller *impl_function_caller = nullptr;
 

                     m_impl_code.reset();
                     return args_addr;
                 }
-                
-                if (!m_impl_code->Install(errors, exe_ctx))
+                if (!m_impl_code->Install(diagnostics, exe_ctx))
                 {
                     if (log)
-                        log->Printf ("Failed to install implementation lookup: %s.", errors.GetData());
+                    {
+                        log->Printf("Failed to install implementation lookup.");
+                        diagnostics.Dump(log);
+                    }
                     m_impl_code.reset();
                     return args_addr;
                 }

             {
                 if (log)
                     log->Printf("No method lookup implementation code.");
-                errors.Printf ("No method lookup implementation code found.");
                 return LLDB_INVALID_ADDRESS;
             }
-            
 
             // Next make the runner function for our implementation utility function.
             ClangASTContext *clang_ast_context = thread.GetProcess()->GetTarget().GetScratchClangASTContext();

             impl_function_caller = m_impl_code->GetFunctionCaller();
         }
     }
-    
-    errors.Clear();
-    
+    diagnostics.Clear();
     // Now write down the argument values for this particular call.  This looks like it might be a race condition
     // if other threads were calling into here, but actually it isn't because we allocate a new args structure for
     // this call by passing args_addr = LLDB_INVALID_ADDRESS...
 
-    if (impl_function_caller->WriteFunctionArguments (exe_ctx, args_addr, dispatch_values, errors))
+    if (impl_function_caller->WriteFunctionArguments(exe_ctx, args_addr, dispatch_values, diagnostics))
     {
         if (log)
-            log->Printf ("Error writing function arguments: \"%s\".", errors.GetData());
+        {
+            log->Printf("Error writing function arguments.");
+            diagnostics.Dump(log);
+        }
         return args_addr;
     }
-        
     return args_addr;
 }
 

source/Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleThreadPlanStepThroughObjCTrampoline.cpp

 // Project includes
 #include "AppleThreadPlanStepThroughObjCTrampoline.h"
 #include "AppleObjCTrampolineHandler.h"
-#include "lldb/Target/Process.h"
-#include "lldb/Target/Thread.h"
+#include "lldb/Core/Log.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/FunctionCaller.h"
 #include "lldb/Expression/UtilityFunction.h"
 #include "lldb/Target/ExecutionContext.h"
 #include "lldb/Target/ObjCLanguageRuntime.h"
+#include "lldb/Target/Process.h"
+#include "lldb/Target/Thread.h"
 #include "lldb/Target/ThreadPlanRunToAddress.h"
 #include "lldb/Target/ThreadPlanStepOut.h"
-#include "lldb/Core/Log.h"
 
-
 using namespace lldb;
 using namespace lldb_private;
 

 {
     if (!m_func_sp)
     {
-        StreamString errors;
+        DiagnosticManager diagnostics;
         m_args_addr = m_trampoline_handler->SetupDispatchFunction(m_thread, m_input_values);
-        
         if (m_args_addr == LLDB_INVALID_ADDRESS)
         {
             return false;

         options.SetIgnoreBreakpoints(true);
         options.SetStopOthers(m_stop_others);
         m_thread.CalculateExecutionContext(exc_ctx);
-        m_func_sp = m_impl_function->GetThreadPlanToCallFunction (exc_ctx,
-                                                                  m_args_addr,
-                                                                  options,
-                                                                  errors);
+        m_func_sp = m_impl_function->GetThreadPlanToCallFunction(exc_ctx, m_args_addr, options, diagnostics);
         m_func_sp->SetOkayToDiscard(true);
-        m_thread.QueueThreadPlan (m_func_sp, false);
+        m_thread.QueueThreadPlan(m_func_sp, false);
     }
     return true;
 }

source/Plugins/Process/Utility/InferiorCallPOSIX.cpp

 #include "lldb/Core/Address.h"
 #include "lldb/Core/StreamFile.h"
 #include "lldb/Core/ValueObject.h"
+#include "lldb/Expression/DiagnosticManager.h"
+#include "lldb/Host/Config.h"
 #include "lldb/Symbol/ClangASTContext.h"
 #include "lldb/Symbol/SymbolContext.h"
 #include "lldb/Target/ExecutionContext.h"

 #include "lldb/Target/Process.h"
 #include "lldb/Target/Target.h"
 #include "lldb/Target/ThreadPlanCallFunction.h"
-#include "lldb/Host/Config.h"
 
 #ifndef LLDB_DISABLE_POSIX
 #include <sys/mman.h>

                 ClangASTContext *clang_ast_context = process->GetTarget().GetScratchClangASTContext();
                 CompilerType clang_void_ptr_type = clang_ast_context->GetBasicType(eBasicTypeVoid).GetPointerType();
                 lldb::addr_t args[] = { addr, length, prot_arg, flags_arg, fd, offset };
-                lldb::ThreadPlanSP call_plan_sp (new ThreadPlanCallFunction (*thread,
-                                                                             mmap_range.GetBaseAddress(),
-                                                                             clang_void_ptr_type,
-                                                                             args,
-                                                                             options));
+                lldb::ThreadPlanSP call_plan_sp(new ThreadPlanCallFunction(*thread, mmap_range.GetBaseAddress(),
+                                                                           clang_void_ptr_type, args, options));
                 if (call_plan_sp)
                 {
-                    StreamFile error_strm;
-                    
-                    StackFrame *frame = thread->GetStackFrameAtIndex (0).get();
+                    DiagnosticManager diagnostics;
+                    StackFrame *frame = thread->GetStackFrameAtIndex(0).get();
                     if (frame)
                     {
                         ExecutionContext exe_ctx;
                         frame->CalculateExecutionContext (exe_ctx);
-                        ExpressionResults result = process->RunThreadPlan (exe_ctx,
-                                                                          call_plan_sp,
-                                                                          options,
-                                                                          error_strm);
+                        ExpressionResults result = process->RunThreadPlan(exe_ctx, call_plan_sp, options, diagnostics);
                         if (result == eExpressionCompleted)
                         {
-                            
                             allocated_addr = call_plan_sp->GetReturnValueObject()->GetValueAsUnsigned(LLDB_INVALID_ADDRESS);
                             if (process->GetAddressByteSize() == 4)
                             {

             if (sc.GetAddressRange(range_scope, 0, use_inline_block_range, munmap_range))
             {
                 lldb::addr_t args[] = { addr, length };
-                lldb::ThreadPlanSP call_plan_sp (new ThreadPlanCallFunction (*thread,
-                                                                            munmap_range.GetBaseAddress(),
-                                                                            CompilerType(),
-                                                                            args,
-                                                                            options));
+                lldb::ThreadPlanSP call_plan_sp(
+                    new ThreadPlanCallFunction(*thread, munmap_range.GetBaseAddress(), CompilerType(), args, options));
                 if (call_plan_sp)
                 {
-                    StreamFile error_strm;
-                   
-                    StackFrame *frame = thread->GetStackFrameAtIndex (0).get();
+                    DiagnosticManager diagnostics;
+                    StackFrame *frame = thread->GetStackFrameAtIndex(0).get();
                     if (frame)
                     {
                         ExecutionContext exe_ctx;
                         frame->CalculateExecutionContext (exe_ctx);
-                        ExpressionResults result = process->RunThreadPlan (exe_ctx,
-                                                                          call_plan_sp,
-                                                                          options,
-                                                                          error_strm);
+                        ExpressionResults result = process->RunThreadPlan(exe_ctx, call_plan_sp, options, diagnostics);
                         if (result == eExpressionCompleted)
                         {
                             return true;

 
     ClangASTContext *clang_ast_context = process->GetTarget().GetScratchClangASTContext();
     CompilerType clang_void_ptr_type = clang_ast_context->GetBasicType(eBasicTypeVoid).GetPointerType();
-    lldb::ThreadPlanSP call_plan_sp (new ThreadPlanCallFunction (*thread,
-                                                                 *address,
-                                                                 clang_void_ptr_type,
-                                                                 llvm::ArrayRef<addr_t>(),
-                                                                 options));
+    lldb::ThreadPlanSP call_plan_sp(
+        new ThreadPlanCallFunction(*thread, *address, clang_void_ptr_type, llvm::ArrayRef<addr_t>(), options));
     if (call_plan_sp)
     {
-        StreamString error_strm;
+        DiagnosticManager diagnostics;
 
-        StackFrame *frame = thread->GetStackFrameAtIndex (0).get();
+        StackFrame *frame = thread->GetStackFrameAtIndex(0).get();
         if (frame)
         {
             ExecutionContext exe_ctx;
             frame->CalculateExecutionContext (exe_ctx);
-            ExpressionResults result = process->RunThreadPlan (exe_ctx,
-                                                              call_plan_sp,
-                                                              options,
-                                                              error_strm);
+            ExpressionResults result = process->RunThreadPlan(exe_ctx, call_plan_sp, options, diagnostics);
             if (result == eExpressionCompleted)
             {
                 returned_func = call_plan_sp->GetReturnValueObject()->GetValueAsUnsigned(LLDB_INVALID_ADDRESS);

source/Plugins/SystemRuntime/MacOSX/AppleGetItemInfoHandler.cpp

 #include "lldb/Core/Module.h"
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/Value.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/FunctionCaller.h"
 #include "lldb/Expression/UtilityFunction.h"
 #include "lldb/Symbol/ClangASTContext.h"

 // make the function call.
 
 lldb::addr_t
-AppleGetItemInfoHandler::SetupGetItemInfoFunction (Thread &thread, ValueList &get_item_info_arglist)
+AppleGetItemInfoHandler::SetupGetItemInfoFunction(Thread &thread, ValueList &get_item_info_arglist)
 {
-    ExecutionContext exe_ctx (thread.shared_from_this());
-    StreamString errors;
-    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_SYSTEM_RUNTIME));
+    ExecutionContext exe_ctx(thread.shared_from_this());
+    DiagnosticManager diagnostics;
+    Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_SYSTEM_RUNTIME));
     lldb::addr_t args_addr = LLDB_INVALID_ADDRESS;
     FunctionCaller *get_item_info_caller = nullptr;
 

                         log->Printf ("Failed to get utility function: %s.", error.AsCString());
                     return args_addr;
                 }
-                
-                if (!m_get_item_info_impl_code->Install(errors, exe_ctx))
+                if (!m_get_item_info_impl_code->Install(diagnostics, exe_ctx))
                 {
                     if (log)
-                        log->Printf ("Failed to install get-item-info introspection: %s.", errors.GetData());
+                    {
+                        log->Printf("Failed to install get-item-info introspection.");
+                        diagnostics.Dump(log);
+                    }
                     m_get_item_info_impl_code.reset();
                     return args_addr;
                 }

             {
                 if (log)
                     log->Printf("No get-item-info introspection code found.");
-                errors.Printf ("No get-item-info introspection code found.");
                 return LLDB_INVALID_ADDRESS;
             }
 

             }
         }
     }
-    
-    errors.Clear();
-    
+    diagnostics.Clear();
     // Now write down the argument values for this particular call.  This looks like it might be a race condition
     // if other threads were calling into here, but actually it isn't because we allocate a new args structure for
     // this call by passing args_addr = LLDB_INVALID_ADDRESS...
 
-    if (!get_item_info_caller->WriteFunctionArguments (exe_ctx, args_addr, get_item_info_arglist, errors))
+    if (!get_item_info_caller->WriteFunctionArguments(exe_ctx, args_addr, get_item_info_arglist, diagnostics))
     {
         if (log)
-            log->Printf ("Error writing get-item-info function arguments: \"%s\".", errors.GetData());
+        {
+            log->Printf("Error writing get-item-info function arguments.");
+            diagnostics.Dump(log);
+        }
+
         return args_addr;
     }
-        
     return args_addr;
 }
 

     page_to_free_size_value.GetScalar() = page_to_free_size;
     argument_values.PushValue (page_to_free_size_value);
 
-    addr_t args_addr = SetupGetItemInfoFunction (thread, argument_values);
+    addr_t args_addr = SetupGetItemInfoFunction(thread, argument_values);
 
-    StreamString errors;
+    DiagnosticManager diagnostics;
     ExecutionContext exe_ctx;
     EvaluateExpressionOptions options;
-    options.SetUnwindOnError (true);
+    options.SetUnwindOnError(true);
     options.SetIgnoreBreakpoints (true);
     options.SetStopOthers (true);
     options.SetTimeoutUsec(500000);

         error.SetErrorString("Could not retrieve function caller for __introspection_dispatch_queue_item_get_info.");
         return return_value;
     }
-    
-    func_call_ret =  func_caller->ExecuteFunction (exe_ctx, &args_addr, options, errors, results);
+    func_call_ret = func_caller->ExecuteFunction(exe_ctx, &args_addr, options, diagnostics, results);
     if (func_call_ret != eExpressionCompleted || !error.Success())
     {
         if (log)

source/Plugins/SystemRuntime/MacOSX/AppleGetPendingItemsHandler.cpp

 #include "lldb/Core/Module.h"
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/Value.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/FunctionCaller.h"
 #include "lldb/Expression/UtilityFunction.h"
 #include "lldb/Symbol/ClangASTContext.h"

 // make the function call.
 
 lldb::addr_t
-AppleGetPendingItemsHandler::SetupGetPendingItemsFunction (Thread &thread, ValueList &get_pending_items_arglist)
+AppleGetPendingItemsHandler::SetupGetPendingItemsFunction(Thread &thread, ValueList &get_pending_items_arglist)
 {
-    ExecutionContext exe_ctx (thread.shared_from_this());
-    StreamString errors;
-    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_SYSTEM_RUNTIME));
+    ExecutionContext exe_ctx(thread.shared_from_this());
+    DiagnosticManager diagnostics;
+    Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_SYSTEM_RUNTIME));
     lldb::addr_t args_addr = LLDB_INVALID_ADDRESS;
     FunctionCaller *get_pending_items_caller = nullptr;
-    
     // Scope for mutex locker:
     {
         Mutex::Locker locker(m_get_pending_items_function_mutex);

                         log->Printf ("Failed to get UtilityFunction for pending-items introspection: %s.", error.AsCString());
                     return args_addr;
                 }
-                
-                if (!m_get_pending_items_impl_code->Install(errors, exe_ctx))
+                if (!m_get_pending_items_impl_code->Install(diagnostics, exe_ctx))
                 {
                     if (log)
-                        log->Printf ("Failed to install pending-items introspection: %s.", errors.GetData());
+                    {
+                        log->Printf("Failed to install pending-items introspection.");
+                        diagnostics.Dump(log);
+                    }
                     m_get_pending_items_impl_code.reset();
                     return args_addr;
                 }

                 return args_addr;
             }
         }
+    }
 
-    }
-    
-    errors.Clear();
-    
+    diagnostics.Clear();
     if (get_pending_items_caller == nullptr)
     {
         if (log)

     // if other threads were calling into here, but actually it isn't because we allocate a new args structure for
     // this call by passing args_addr = LLDB_INVALID_ADDRESS...
 
-    if (!get_pending_items_caller->WriteFunctionArguments (exe_ctx, args_addr, get_pending_items_arglist, errors))
+    if (!get_pending_items_caller->WriteFunctionArguments(exe_ctx, args_addr, get_pending_items_arglist, diagnostics))
     {
         if (log)
-            log->Printf ("Error writing pending-items function arguments: \"%s\".", errors.GetData());
+        {
+            log->Printf("Error writing pending-items function arguments.");
+            diagnostics.Dump(log);
+        }
+
         return args_addr;
     }
-        
     return args_addr;
 }
 

     page_to_free_size_value.GetScalar() = page_to_free_size;
     argument_values.PushValue (page_to_free_size_value);
 
-    addr_t args_addr = SetupGetPendingItemsFunction (thread, argument_values);
+    addr_t args_addr = SetupGetPendingItemsFunction(thread, argument_values);
 
-    StreamString errors;
+    DiagnosticManager diagnostics;
     ExecutionContext exe_ctx;
     FunctionCaller *get_pending_items_caller = m_get_pending_items_impl_code->GetFunctionCaller();
-    
     EvaluateExpressionOptions options;
     options.SetUnwindOnError (true);
     options.SetIgnoreBreakpoints (true);

         return return_value;
     }
 
-
     ExpressionResults func_call_ret;
     Value results;
-    func_call_ret =  get_pending_items_caller->ExecuteFunction (exe_ctx, &args_addr, options, errors, results);
+    func_call_ret = get_pending_items_caller->ExecuteFunction(exe_ctx, &args_addr, options, diagnostics, results);
     if (func_call_ret != eExpressionCompleted || !error.Success())
     {
         if (log)

source/Plugins/SystemRuntime/MacOSX/AppleGetQueuesHandler.cpp

 #include "lldb/Core/Module.h"
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/Value.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/FunctionCaller.h"
 #include "lldb/Expression/UtilityFunction.h"
 #include "lldb/Symbol/ClangASTContext.h"

 lldb::addr_t
 AppleGetQueuesHandler::SetupGetQueuesFunction (Thread &thread, ValueList &get_queues_arglist)
 {
-    ExecutionContext exe_ctx (thread.shared_from_this());
+    ExecutionContext exe_ctx(thread.shared_from_this());
     Address impl_code_address;
-    StreamString errors;
-    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_SYSTEM_RUNTIME));
+    DiagnosticManager diagnostics;
+    Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_SYSTEM_RUNTIME));
     lldb::addr_t args_addr = LLDB_INVALID_ADDRESS;
-    
     FunctionCaller *get_queues_caller = nullptr;
 
     // Scope for mutex locker:

                         log->Printf ("Failed to get UtilityFunction for queues introspection: %s.", error.AsCString());
                     return args_addr;
                 }
-                
-                if (!m_get_queues_impl_code_up->Install(errors, exe_ctx))
+                if (!m_get_queues_impl_code_up->Install(diagnostics, exe_ctx))
                 {
                     if (log)
-                        log->Printf ("Failed to install queues introspection: %s.", errors.GetData());
+                    {
+                        log->Printf("Failed to install queues introspection");
+                        diagnostics.Dump(log);
+                    }
                     m_get_queues_impl_code_up.reset();
                     return args_addr;
                 }

             else
             {
                 if (log)
+                {
                     log->Printf("No queues introspection code found.");
-                errors.Printf ("No queues introspection code found.");
+                    diagnostics.Dump(log);
+                }
                 return LLDB_INVALID_ADDRESS;
             }
         }
-        
         // Next make the runner function for our implementation utility function.
         ClangASTContext *clang_ast_context = thread.GetProcess()->GetTarget().GetScratchClangASTContext();
         CompilerType get_queues_return_type = clang_ast_context->GetBasicType(eBasicTypeVoid).GetPointerType();

             return args_addr;
         }
     }
-    
-    errors.Clear();
-    
+    diagnostics.Clear();
     // Now write down the argument values for this particular call.  This looks like it might be a race condition
     // if other threads were calling into here, but actually it isn't because we allocate a new args structure for
     // this call by passing args_addr = LLDB_INVALID_ADDRESS...
 
-    if (!get_queues_caller->WriteFunctionArguments (exe_ctx, args_addr, get_queues_arglist, errors))
+    if (!get_queues_caller->WriteFunctionArguments(exe_ctx, args_addr, get_queues_arglist, diagnostics))
     {
         if (log)
-            log->Printf ("Error writing get-queues function arguments: \"%s\".", errors.GetData());
+        {
+            log->Printf("Error writing get-queues function arguments.");
+            diagnostics.Dump(log);
+        }
         return args_addr;
     }
-        
     return args_addr;
 }
 

         return return_value;
     }
 
-    StreamString errors;
+    DiagnosticManager diagnostics;
     ExecutionContext exe_ctx;
     EvaluateExpressionOptions options;
-    options.SetUnwindOnError (true);
+    options.SetUnwindOnError(true);
     options.SetIgnoreBreakpoints (true);
     options.SetStopOthers (true);
     options.SetTimeoutUsec(500000);

 
     ExpressionResults func_call_ret;
     Value results;
-    func_call_ret =  get_queues_caller->ExecuteFunction (exe_ctx, &args_addr, options, errors, results);
+    func_call_ret = get_queues_caller->ExecuteFunction(exe_ctx, &args_addr, options, diagnostics, results);
     if (func_call_ret != eExpressionCompleted || !error.Success())
     {
         if (log)

source/Plugins/SystemRuntime/MacOSX/AppleGetThreadItemInfoHandler.cpp

 // Other libraries and framework includes
 // Project includes
 
-#include "lldb/lldb-private.h"
 #include "lldb/Core/ConstString.h"
 #include "lldb/Core/Log.h"
 #include "lldb/Core/Module.h"
 #include "lldb/Core/StreamString.h"
 #include "lldb/Core/Value.h"
+#include "lldb/Expression/DiagnosticManager.h"
 #include "lldb/Expression/Expression.h"
 #include "lldb/Expression/FunctionCaller.h"
 #include "lldb/Expression/UtilityFunction.h"

 #include "lldb/Target/StackFrame.h"
 #include "lldb/Target/Target.h"
 #include "lldb/Target/Thread.h"
+#include "lldb/lldb-private.h"
 
 using namespace lldb;
 using namespace lldb_private;

 lldb::addr_t
 AppleGetThreadItemInfoHandler::SetupGetThreadItemInfoFunction (Thread &thread, ValueList &get_thread_item_info_arglist)
 {
-    ExecutionContext exe_ctx (thread.shared_from_this());
+    ExecutionContext exe_ctx(thread.shared_from_this());
     Address impl_code_address;
-    StreamString errors;
-    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_SYSTEM_RUNTIME));
+    DiagnosticManager diagnostics;
+    Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_SYSTEM_RUNTIME));
     lldb::addr_t args_addr = LLDB_INVALID_ADDRESS;
     FunctionCaller *get_thread_item_info_caller = nullptr;
 

                     m_get_thread_item_info_impl_code.reset();
                     return args_addr;
                 }
-                
-                if (!m_get_thread_item_info_impl_code->Install(errors, exe_ctx))
+                if (!m_get_thread_item_info_impl_code->Install(diagnostics, exe_ctx))
                 {
                     if (log)
-                        log->Printf ("Failed to install get-thread-item-info introspection: %s.", errors.GetData());
+                    {
+                        log->Printf("Failed to install get-thread-item-info introspection.");
+                        diagnostics.Dump(log);
+                    }
+
                     m_get_thread_item_info_impl_code.reset();
                     return args_addr;
                 }

             {
                 if (log)
                     log->Printf("No get-thread-item-info introspection code found.");
-                errors.Printf ("No get-thread-item-info introspection code found.");
                 return LLDB_INVALID_ADDRESS;
             }
-            
             // Also make the FunctionCaller for this UtilityFunction:
             
             ClangASTContext *clang_ast_context = thread.GetProcess()->GetTarget().GetScratchClangASTContext();

             get_thread_item_info_caller = m_get_thread_item_info_impl_code->GetFunctionCaller();
         }
     }
-    
-    errors.Clear();
-    
+    diagnostics.Clear();
     // Now write down the argument values for this particular call.  This looks like it might be a race condition
     // if other threads were calling into here, but actually it isn't because we allocate a new args structure for
     // this call by passing args_addr = LLDB_INVALID_ADDRESS...
 
-    if (!get_thread_item_info_caller->WriteFunctionArguments (exe_ctx, args_addr, get_thread_item_info_arglist, errors))
+    if (!get_thread_item_info_caller->WriteFunctionArguments(exe_ctx, args_addr, get_thread_item_info_arglist,
+                                                             diagnostics))
     {
         if (log)
-            log->Printf ("Error writing get-thread-item-info function arguments: \"%s\".", errors.GetData());
+        {
+            log->Printf("Error writing get-thread-item-info function arguments");
+            diagnostics.Dump(log);
+        }
         return args_addr;
     }
-        
     return args_addr;
 }
 

     page_to_free_size_value.GetScalar() = page_to_free_size;
     argument_values.PushValue (page_to_free_size_value);
 
-    addr_t args_addr = SetupGetThreadItemInfoFunction (thread, argument_values);
+    addr_t args_addr = SetupGetThreadItemInfoFunction(thread, argument_values);
 
-    StreamString errors;
+    DiagnosticManager diagnostics;
     ExecutionContext exe_ctx;
     EvaluateExpressionOptions options;
     FunctionCaller *get_thread_item_info_caller = nullptr;
-    
     options.SetUnwindOnError (true);
     options.SetIgnoreBreakpoints (true);
     options.SetStopOthers (true);

 
     ExpressionResults func_call_ret;
     Value results;
-    func_call_ret =  get_thread_item_info_caller->ExecuteFunction (exe_ctx, &args_addr, options, errors, results);
+    func_call_ret = get_thread_item_info_caller->ExecuteFunction(exe_ctx, &args_addr, options, diagnostics, results);
     if (func_call_ret != eExpressionCompleted || !error.Success())
     {
         if (log)

source/Symbol/ClangASTContext.cpp

     {
         m_log = lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS);
     }
-    
-    void HandleDiagnostic (DiagnosticsEngine::Level DiagLevel, const Diagnostic &info)
+    void
+    HandleDiagnostic(DiagnosticsEngine::Level DiagLevel, const clang::Diagnostic &info)
     {
         if (m_log)
         {

source/Target/Process.cpp

 
 // Other libraries and framework includes
 // Project includes
-#include "lldb/Target/Process.h"
+#include "Plugins/Process/Utility/InferiorCallPOSIX.h"
+#include "lldb/Breakpoint/BreakpointLocation.h"
 #include "lldb/Breakpoint/StoppointCallbackContext.h"
-#include "lldb/Breakpoint/BreakpointLocation.h"
+#include "lldb/Core/Debugger.h"
 #include "lldb/Core/Event.h"
-#include "lldb/Core/Debugger.h"
 #include "lldb/Core/Log.h"
 #include "lldb/Core/Module.h"
 #include "lldb/Core/ModuleSpec.h"
 #include "lldb/Core/PluginManager.h"
 #include "lldb/Core/State.h"
 #include "lldb/Core/StreamFile.h"
+#include "lldb/Expression/DiagnosticManager.h"
+#include "lldb/Expression/IRDynamicChecks.h"
 #include "lldb/Expression/UserExpression.h"
-#include "lldb/Expression/IRDynamicChecks.h"
 #include "lldb/Host/ConnectionFileDescriptor.h"
 #include "lldb/Host/FileSystem.h"
 #include "lldb/Host/Host.h"

 #include "lldb/Symbol/Function.h"
 #include "lldb/Symbol/Symbol.h"
 #include "lldb/Target/ABI.h"
+#include "lldb/Target/CPPLanguageRuntime.h"
 #include "lldb/Target/DynamicLoader.h"
 #include "lldb/Target/InstrumentationRuntime.h"
 #include "lldb/Target/JITLoader.h"
 #include "lldb/Target/JITLoaderList.h"
+#include "lldb/Target/LanguageRuntime.h"
 #include "lldb/Target/MemoryHistory.h"
 #include "lldb/Target/MemoryRegionInfo.h"
+#include "lldb/Target/ObjCLanguageRuntime.h"
 #include "lldb/Target/OperatingSystem.h"
-#include "lldb/Target/LanguageRuntime.h"
-#include "lldb/Target/CPPLanguageRuntime.h"
-#include "lldb/Target/ObjCLanguageRuntime.h"
 #include "lldb/Target/Platform.h"
+#include "lldb/Target/Process.h"
 #include "lldb/Target/RegisterContext.h"
 #include "lldb/Target/StopInfo.h"
 #include "lldb/Target/SystemRuntime.h"

 #include "lldb/Target/ThreadPlanBase.h"
 #include "lldb/Target/UnixSignals.h"
 #include "lldb/Utility/NameMatches.h"
-#include "Plugins/Process/Utility/InferiorCallPOSIX.h"
 
 using namespace lldb;
 using namespace lldb_private;

 } // anonymous namespace
 
 ExpressionResults
-Process::RunThreadPlan (ExecutionContext &exe_ctx,
-                        lldb::ThreadPlanSP &thread_plan_sp,
-                        const EvaluateExpressionOptions &options,
-                        Stream &errors)
+Process::RunThreadPlan(ExecutionContext &exe_ctx, lldb::ThreadPlanSP &thread_plan_sp,
+                       const EvaluateExpressionOptions &options, DiagnosticManager &diagnostic_manager)
 {
     ExpressionResults return_value = eExpressionSetupError;
 
     if (!thread_plan_sp)
     {
-        errors.Printf("RunThreadPlan called with empty thread plan.");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "RunThreadPlan called with empty thread plan.");
         return eExpressionSetupError;
     }
 
     if (!thread_plan_sp->ValidatePlan(nullptr))
     {
-        errors.Printf ("RunThreadPlan called with an invalid thread plan.");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "RunThreadPlan called with an invalid thread plan.");
         return eExpressionSetupError;
     }
 
     if (exe_ctx.GetProcessPtr() != this)
     {
-        errors.Printf("RunThreadPlan called on wrong process.");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "RunThreadPlan called on wrong process.");
         return eExpressionSetupError;
     }
 
     Thread *thread = exe_ctx.GetThreadPtr();
     if (thread == nullptr)
     {
-        errors.Printf("RunThreadPlan called with invalid thread.");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError, "RunThreadPlan called with invalid thread.");
         return eExpressionSetupError;
     }
 

 
     if (m_private_state.GetValue() != eStateStopped)
     {
-        errors.Printf ("RunThreadPlan called while the private state was not stopped.");
+        diagnostic_manager.PutCString(eDiagnosticSeverityError,
+                                      "RunThreadPlan called while the private state was not stopped.");
         return eExpressionSetupError;
     }
 

         selected_frame_sp = thread->GetSelectedFrame();
         if (!selected_frame_sp)
         {
-            errors.Printf("RunThreadPlan called without a selected frame on thread %d", thread_idx_id);
+            diagnostic_manager.Printf(eDiagnosticSeverityError,
+                                      "RunThreadPlan called without a selected frame on thread %d", thread_idx_id);
             return eExpressionSetupError;
         }
     }

                 {
                     if (timeout_usec < option_one_thread_timeout)
                     {
-                        errors.Printf("RunThreadPlan called without one thread timeout greater than total timeout");
+                        diagnostic_manager.PutCString(
+                            eDiagnosticSeverityError,
+                            "RunThreadPlan called without one thread timeout greater than total timeout");
                         return eExpressionSetupError;
                     }
                     computed_one_thread_timeout = option_one_thread_timeout;

         Event *other_events = listener_sp->PeekAtNextEvent();
         if (other_events != nullptr)
         {
-            errors.Printf("Calling RunThreadPlan with pending events on the queue.");
+            diagnostic_manager.PutCString(eDiagnosticSeverityError,
+                                          "RunThreadPlan called with pending events on the queue.");
             return eExpressionSetupError;
         }
 

                 if (do_resume)
                 {
                     num_resumes++;
-                    Error resume_error = PrivateResume ();
+                    Error resume_error = PrivateResume();
                     if (!resume_error.Success())
                     {
-                        errors.Printf("Error resuming inferior the %d time: \"%s\".\n",
-                                      num_resumes,
+                        diagnostic_manager.Printf(eDiagnosticSeverityError,
+                                                  "couldn't resume inferior the %d time: \"%s\".", num_resumes,
                                                   resume_error.AsCString());
                         return_value = eExpressionSetupError;
                         break;
                     }

                 if (!got_event)
                 {
                     if (log)
-                        log->Printf ("Process::RunThreadPlan(): didn't get any event after resume %d, exiting.",
-                                        num_resumes);
+                        log->Printf("Process::RunThreadPlan(): didn't get any event after resume %" PRIu32 ", exiting.",
 
-                    errors.Printf("Didn't get any event after resume %d, exiting.", num_resumes);
+                    diagnostic_manager.Printf(eDiagnosticSeverityError,
+                                              "didn't get any event after resume %" PRIu32 ", exiting.", num_resumes);
                     return_value = eExpressionSetupError;
                     break;
                 }

                         Halt(clear_thread_plans, use_run_lock);
                     }
 
-                    errors.Printf("Didn't get running event after initial resume, got %s instead.",
-                                  StateAsCString(stop_state));
+                    diagnostic_manager.Printf(eDiagnosticSeverityError,
+                                              "didn't get running event after initial resume, got %s instead.",
+                                              StateAsCString(stop_state));
                     return_value = eExpressionSetupError;
                     break;
                 }

                         const bool use_run_lock = false;
                         Halt(clear_thread_plans, use_run_lock);
                         return_value = eExpressionInterrupted;
-                        errors.Printf ("Execution halted by user interrupt.");
+                        diagnostic_manager.PutCString(eDiagnosticSeverityRemark, "execution halted by user interrupt.");
                         if (log)
-                            log->Printf ("Process::RunThreadPlan(): Got  interrupted by eBroadcastBitInterrupted, exiting.");
+                            log->Printf(
+                                "Process::RunThreadPlan(): Got  interrupted by eBroadcastBitInterrupted, exiting.");
                         break;
                     }
                     else

                             if (stop_state == eStateExited)
                                 event_to_broadcast_sp = event_sp;
 
-                            errors.Printf ("Execution stopped with unexpected state.\n");
+                            diagnostic_manager.PutCString(eDiagnosticSeverityError,
+                                                          "execution stopped with unexpected state.");
                             return_value = eExpressionInterrupted;
                             break;
                         }

source/Target/ThreadPlanCallUserExpression.cpp

 #include "lldb/Core/Address.h"
 #include "lldb/Core/Log.h"
 #include "lldb/Core/Stream.h"
+#include "lldb/Expression/DiagnosticManager.h"
+#include "lldb/Expression/IRDynamicChecks.h"
 #include "lldb/Expression/UserExpression.h"
-#include "lldb/Expression/IRDynamicChecks.h"
 #include "lldb/Host/HostInfo.h"
 #include "lldb/Target/LanguageRuntime.h"
 #include "lldb/Target/Process.h"

 
             function_stack_bottom = function_stack_pointer - HostInfo::GetPageSize();
             function_stack_top = function_stack_pointer;
-            
-            StreamString  error_stream;
-            
+            DiagnosticManager diagnostics;
             ExecutionContext exe_ctx(GetThread());
 
-            m_user_expression_sp->FinalizeJITExecution(error_stream, exe_ctx, m_result_var_sp, function_stack_bottom, function_stack_top);
+            m_user_expression_sp->FinalizeJITExecution(diagnostics, exe_ctx, m_result_var_sp, function_stack_bottom,
+                                                       function_stack_top);
         }
-        
-        ThreadPlan::MischiefManaged ();
+        ThreadPlan::MischiefManaged();
         return true;
     }
     else