Add auto deduce source map setting

[yinghuitan]

Summary

This patch adds a new "target.auto-deduce-source-map" setting.

If enabled, this setting may auto deduce a source map entry based on requested
breakpoint path and the original path stored in debug info for resolved
breakpoint.

As an example, if debug info contains "./a/b/c/main.cpp", user sets a source
breakpoint at "/root/repo/x/y/z/a/b/c/main.cpp". The breakpoint will resolve
correctly now with Greg's patch https://reviews.llvm.org/D130401. However, the
resolved breakpoint will use "./a/b/c/main.cpp" to locate source file during
stop event which would fail most of the time.

With the new "target.auto-deduce-source-map" setting enabled, a auto deduced
source map entry "." => "/root/repo/x/y/z" will be added. This new mapping will
help lldb to map resolved breakpoint path "./a/b/c/main.cpp" back to
"/root/repo/x/y/z/a/b/c/main.cpp" and locate it on disk.

If an existing source map entry is used the patch also concatenates the auto
deduced entry with any stripped reverse mapping prefix (see example below).

As a second example, debug info contains "./a/b/c/main.cpp" and user sets
breakpoint at "/root/repo/x/y/z/a/b/c/main.cpp". Let's say there is an existing
source map entry "." => "/root/repo"; this mapping would strip the prefix out of
"/root/repo/x/y/z/a/b/c/main.cpp" and use "x/y/z/a/b/c/main.cpp" to resolve
breakpoint. "target.auto-deduce-source-map" setting would auto deduce a new
potential mapping of "." => "x/y/z", then it detects that there is a stripped
prefix from reverse mapping and concatenates it as the new mapping:
"." => "/root/repo/x/y/z" which would correct map "./a/b/c/main.cpp" path to
new path in disk.

This patches depends on https://reviews.llvm.org/D133038 to use new added
SBTarget::GetSourceMap() API for testing.

[clayborg]

The main question for me here is if "target.auto-deduce-source-map" should be a boolean or an enum. This path, if I read it correctly, will only auto deduce source maps if the debug info contains relative paths and a full path is specified. So maybe it should be:

(lldb) settings set target.auto-deduce-source-map disabled
(lldb) settings set target.auto-deduce-source-map relative-debug-info

If we plan to use the target.auto-deduce-source-map to later handle cases where we have two different full paths, the user might not want to enable this setting.

Or we can clarify that this setting deduces source mapping only for relative debug info paths by renaming it and then the "bool" value makes more sense?

lldb/include/lldb/Breakpoint/BreakpointResolverFileLine.h

28

69

Store this as a weak pointer to a target to avoid a target that owns an object that will keep the target object from ever being able to destruct itself. Anytime you need to use the target then you use a local variable that is a shared pointer:

TargetSP target_sp = m_target_wp.lock();
if (!target_sp)
  return;

70

Remove this. No need to store this as a member variable, just ask the breakpoints target for it when you need it since you only use this once.

lldb/source/Breakpoint/BreakpointResolverFileLine.cpp

31

Remove this and use target when needed on demand.

195–196

215

Can we just return if m_location_spec.IsRelative() returns true here to short circuit this entire function? Many users type "b main.cpp:12" and we probably don't need to do any auto source map stuff if the request starts as a relative path like "main.cpp" or "foo/bar/baz.cpp" right?

215

Move the "request_file" below to this line and use it to avoid copying it each time through the loop.

220

Should we quickly continue here if "sc_file" is not relative?

223

Move this out of the for loop. No need to calculate it each time.

237

please use the llvm::sys::path::append stuff to append paths to each other so it can worry about adding any needed directory delimiters

244

If it is empty, then assign

250

use llvm::sys::path::append

305

I would remove this check and just call DeduceSourceMapping all the time and check for this setting in the function itself.

lldb/source/Target/PathMappingList.cpp

82–83

Call Normalize on "path" and "replacement" outside of this loop instead of doing it each time through

[yinghuitan]

@clayborg , it is my intention to make target.auto-deduce-source-map boolean flag ultimately working for both relative paths and two full paths (two full paths are really important for off build host debugging, e.g. dump or production debugging). In this patch, I focuses on getting relative path working because that's the default behavior; a follow-up patch can get two full paths working.
In my opinion boolean flag setting is dead simple to use (to enable both) and an enumeration setting would add extra barrier for adoption.

I can add description to target.auto-deduce-source-map to explain it only works for relative paths.

lldb/include/lldb/Breakpoint/BreakpointResolverFileLine.h

69

Your later comment reminds me that we can get target from GetBreakpoint()->GetTarget() so we do not need to store target point at all.

lldb/source/Breakpoint/BreakpointResolverFileLine.cpp

215

I do not think we can because if an existing reverse source mapping is applied m_location_spec will become a relative path even though original request is full path (Remember the prefix is stripped and stored in removed_prefix_opt? )

I guess I can check:

1. If removed_prefix_opt is not available, then return if m_location_spec.IsRelative() is true.
2. If removed_prefix_opt is available, do nothing.

220

I do not think so. Here is an example:

dwarf sc_file:
/build/repo/x/y/z/foo.cpp

breakpoint request:
/user/root/new_repo_location/x/y/z/foo.cpp

User has an existing source mapping entry so a reverse mapping is applied:
original: .
replacement: /user/root/new_repo_location

After reverse mapping:
Breakpoint::m_location_spec: x/y/z/foo.cpp

With the new auto-deduce-source-map a new source mapping entry is added:
original: /build/repo
replacement: /user/root/new_repo_location

You can see the sc_list is full path in this example.

[yinghuitan]

Address review comments

[clayborg]

In D133042#3791146, @yinghuitan wrote:

@clayborg , it is my intention to make target.auto-deduce-source-map boolean flag ultimately working for both relative paths and two full paths (two full paths are really important for off build host debugging, e.g. dump or production debugging). In this patch, I focuses on getting relative path working because that's the default behavior; a follow-up patch can get two full paths working.
In my opinion boolean flag setting is dead simple to use (to enable both) and an enumeration setting would add extra barrier for adoption.

So I think we should have two settings if this is the case. Why? Because I think the default values for "target.auto-deduce-source-map" should be true for relative paths in debug info, but not true by default for two different full paths in the debug info. We have no way to doing a great job at trying to match up two different full paths. What if we have "/a/b/c/foo.cpp" and "/d/e/f/foo.cpp". If this setting is enabled, I don't expect us to make an auto source map between "/a/b/c" -> "/d/e/f". We would need to specify a minimum directory depth and that gets really messy and involved more settings, and I don't think the full path stuff should be enabled by default.

I can add description to target.auto-deduce-source-map to explain it only works for relative paths.

So not sure if we need to rename this setting to something like "target.auto-source-map-relative" to make this clear, and then this can and should default to true. Then if we later add full path remapping we can use "target.auto-source-map-absolute" and default it to false, and there will need to be many other settings for directory depth and other things. I just think there is too much that can go wrong with the auto remapping of full paths to group them both into the same bucket. I would also rather teach the production build toolchains to emit relative debug info and then never have to add the really hard auto source maps for different paths. That is unless we expose the DW_AT_comp_dir value in lldb_private::CompileUnit and can make a rock solid auto path mapping tool from those settings.

lldb/source/Breakpoint/BreakpointResolverFileLine.cpp

225

If the directory is empty on the requested file, should we be doing anything here? Can we early return?

305

See my inline comment below, but the BreakpointResolverFileLine is created with a NULL for the breakpoint. Does the breakpoint get set properly prior any of these calls? I am sure it must?

lldb/source/Target/Target.cpp

405

The breakpoint is initialized with NULL here. Does it get set to something valid before we try to use it somehow? I am worried we won't be able to get a target from the BreakpointResolver's stored breakpoint????

lldb/source/Target/TargetProperties.td

40

41

42

[yinghuitan]

@clayborg, now I see you want to make this option true by default while full paths one to be optional. Then sure, it makes sense.

lldb/source/Breakpoint/BreakpointResolverFileLine.cpp

225

This should be handled by check at line 221, right? If request_file.GetDirectory().IsEmpty() then request_file.IsRelative() should be true and early return already?

lldb/source/Target/Target.cpp

405

It is initialized as nullptr here but CreateBreakpoint() call in next line will call BreakpointResolver::SetBreakpoint() to initialize it. Actually in BreakpointResolver::GetBreakpoint() explicitly has an assertion to ensure it can't be nullptr so I assume we should be safe here.

[clayborg]

lldb/source/Breakpoint/BreakpointResolverFileLine.cpp

225

Then you can just set full to true all the time then right?

lldb/source/Target/Target.cpp

405

Sounds good. I looked around the code. Looks like the breakpoint in the constructor is used for the "create from StructuredData".

[yinghuitan]

Address review feedback

[clayborg]

Just one nit about double checking if auto deducing is enabled. Fix that and this is good to go.

lldb/source/Breakpoint/BreakpointResolverFileLine.cpp

305

Either remove this, or leave the check in the DeduceSourceMapping function. I would vote to just always call DeduceSourceMapping in case someone else calls it from anywhere else.

[yinghuitan]

Fix nit

lldb/include/lldb/Breakpoint/BreakpointResolverFileLine.h

 
 /// \class BreakpointResolverFileLine BreakpointResolverFileLine.h
 /// "lldb/Breakpoint/BreakpointResolverFileLine.h" This class sets breakpoints
 /// by file and line.  Optionally, it will look for inlined instances of the
 /// file and line specification.
 
 class BreakpointResolverFileLine : public BreakpointResolver {
 public:
-  BreakpointResolverFileLine(const lldb::BreakpointSP &bkpt,
-                             lldb::addr_t offset, bool skip_prologue,
-                             const SourceLocationSpec &location_spec);
+  BreakpointResolverFileLine(
+      const lldb::BreakpointSP &bkpt, lldb::addr_t offset, bool skip_prologue,
+      const SourceLocationSpec &location_spec,
+      llvm::Optional<llvm::StringRef> removed_prefix_opt = llvm::None);
 
   static BreakpointResolver *
   CreateFromStructuredData(const lldb::BreakpointSP &bkpt,
                            const StructuredData::Dictionary &data_dict,
                            Status &error);
 
   StructuredData::ObjectSP SerializeToStructuredData() override;
 
   ~BreakpointResolverFileLine() override = default;
static inline bool classof(const BreakpointResolver *V) {
     return V->getResolverID() == BreakpointResolver::FileLineResolver;
   }
 
   lldb::BreakpointResolverSP
   CopyForBreakpoint(lldb::BreakpointSP &breakpoint) override;
 
 protected:
   void FilterContexts(SymbolContextList &sc_list);
+  void DeduceSourceMapping(SymbolContextList &sc_list);
 
   friend class Breakpoint;
   SourceLocationSpec m_location_spec;
   bool m_skip_prologue;
+  // Any previously removed file path prefix by reverse source mapping.
+  // This is used to auto deduce source map if needed.
+  llvm::Optional<llvm::StringRef> m_removed_prefix_opt;
 
 private:
   BreakpointResolverFileLine(const BreakpointResolverFileLine &) = delete;
   const BreakpointResolverFileLine &
   operator=(const BreakpointResolverFileLine &) = delete;
 };
 
 } // namespace lldb_private
 
 #endif // LLDB_BREAKPOINT_BREAKPOINTRESOLVERFILELINE_H

lldb/include/lldb/Target/PathMappingList.h

public:
   ~PathMappingList();
 
   const PathMappingList &operator=(const PathMappingList &rhs);
 
   void Append(llvm::StringRef path, llvm::StringRef replacement, bool notify);
 
   void Append(const PathMappingList &rhs, bool notify);
 
+  void AppendUnique(llvm::StringRef path, llvm::StringRef replacement,
+                    bool notify);
+
   void Clear(bool notify);
 
   // By default, dump all pairs.
   void Dump(Stream *s, int pair_index = -1);
 
   llvm::json::Value ToJSON();
 
   bool IsEmpty() const { return m_pairs.empty(); }
public:
   ///     checked.
   ///
   /// \return
   ///     The remapped filespec that may or may not exist on disk.
   llvm::Optional<FileSpec> RemapPath(llvm::StringRef path,
                                      bool only_if_exists = false) const;
   bool RemapPath(const char *, std::string &) const = delete;
 
-  bool ReverseRemapPath(const FileSpec &file, FileSpec &fixed) const;
+  /// Perform reverse source path remap for input \a file.
+  /// Source maps contains a list of <from_original_path, to_new_path> mappings.
+  /// Reverse remap means locating a matching entry prefix using "to_new_path"
+  /// part and replacing it with "from_original_path" part if found.
+  ///
+  /// \param[in] file
+  ///     The source path to reverse remap.
+  /// \param[in] fixed
+  ///     The reversed mapped new path.
+  ///
+  /// \return
+  ///     llvm::None if no remapping happens, otherwise, the matching source map
+  ///     entry's ""to_new_pathto"" part (which is the prefix of \a file) is
+  ///     returned.
+  llvm::Optional<llvm::StringRef> ReverseRemapPath(const FileSpec &file,
+                                                   FileSpec &fixed) const;
 
   /// Finds a source file given a file spec using the path remappings.
   ///
   /// Tries to resolve \a orig_spec by checking the path remappings.
   /// It makes sure the file exists by checking with the file system,
   /// so this call can be expensive if the remappings are on a network
   /// or are even on the local file system, so use this function
   /// sparingly (not in a tight debug info parsing loop).

lldb/include/lldb/Target/Target.h

public:
   Environment GetTargetEnvironment() const;
   // Set the target specific environment.
   void SetEnvironment(Environment env);
 
   bool GetSkipPrologue() const;
 
   PathMappingList &GetSourcePathMap() const;
 
+  bool GetAutoSourceMapRelative() const;
+
   FileSpecList GetExecutableSearchPaths();
 
   void AppendExecutableSearchPaths(const FileSpec &);
 
   FileSpecList GetDebugFileSearchPaths();
 
   FileSpecList GetClangModuleSearchPaths();
 

lldb/source/Breakpoint/BreakpointResolverFileLine.cpp

 //===-- BreakpointResolverFileLine.cpp ------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "lldb/Breakpoint/BreakpointResolverFileLine.h"
 
 #include "lldb/Breakpoint/BreakpointLocation.h"
 #include "lldb/Core/Module.h"
 #include "lldb/Symbol/CompileUnit.h"
 #include "lldb/Symbol/Function.h"
+#include "lldb/Target/Target.h"
 #include "lldb/Utility/LLDBLog.h"
 #include "lldb/Utility/Log.h"
 #include "lldb/Utility/StreamString.h"
 
 using namespace lldb;
 using namespace lldb_private;
 
 // BreakpointResolverFileLine:
 BreakpointResolverFileLine::BreakpointResolverFileLine(
     const BreakpointSP &bkpt, lldb::addr_t offset, bool skip_prologue,
-    const SourceLocationSpec &location_spec)
+    const SourceLocationSpec &location_spec,
+    llvm::Optional<llvm::StringRef> removed_prefix_opt)
     : BreakpointResolver(bkpt, BreakpointResolver::FileLineResolver, offset),
-      m_location_spec(location_spec), m_skip_prologue(skip_prologue) {}
+      m_location_spec(location_spec), m_skip_prologue(skip_prologue),
+      m_removed_prefix_opt(removed_prefix_opt) {}
 
 BreakpointResolver *BreakpointResolverFileLine::CreateFromStructuredData(
     const BreakpointSP &bkpt, const StructuredData::Dictionary &options_dict,
     Status &error) {
   llvm::StringRef filename;
   uint32_t line;
   uint16_t column;
   bool check_inlines;
   bool skip_prologue;
if (line &&
         m_location_spec.GetLine() < line - decl_line_is_too_late_fudge) {
       LLDB_LOG(log, "removing symbol context at {0}:{1}", file, line);
       sc_list.RemoveContextAtIndex(i);
       --i;
     }
   }
 }
 
+void BreakpointResolverFileLine::DeduceSourceMapping(
+    SymbolContextList &sc_list) {
+  Target &target = GetBreakpoint()->GetTarget();
+  if (!target.GetAutoSourceMapRelative())
+    return;
+
+  Log *log = GetLog(LLDBLog::Breakpoints);
+  const llvm::StringRef path_separator = llvm::sys::path::get_separator(
+      m_location_spec.GetFileSpec().GetPathStyle());
+  // Check if "b" is a suffix of "a".
+  // And return llvm::None if not or the new path
+  // of "a" after consuming "b" from the back.
+  auto check_suffix =
+      [path_separator](llvm::StringRef a, llvm::StringRef b,
+                       bool case_sensitive) -> llvm::Optional<llvm::StringRef> {
+    if (case_sensitive ? a.consume_back(b) : a.consume_back_insensitive(b)) {
+      if (a.empty() || a.endswith(path_separator)) {
+        return a;
+      }
+    }
+    return llvm::None;
+  };
+
+  FileSpec request_file = m_location_spec.GetFileSpec();
+
+  // Only auto deduce source map if breakpoint is full path.
+  // Note: an existing source map reverse mapping (m_removed_prefix_opt has
+  // value) may make request_file relative.
+  if (!m_removed_prefix_opt.has_value() && request_file.IsRelative())
+    return;
+
+  const bool case_sensitive = request_file.IsCaseSensitive();
+  for (uint32_t i = 0; i < sc_list.GetSize(); ++i) {
+    SymbolContext sc;
+    sc_list.GetContextAtIndex(i, sc);
+
+    FileSpec sc_file = sc.line_entry.file;
+
+    if (FileSpec::Equal(sc_file, request_file, /*full*/true))
+      continue;
+
+    llvm::StringRef sc_file_dir = sc_file.GetDirectory().GetStringRef();
+    llvm::StringRef request_file_dir =
+        request_file.GetDirectory().GetStringRef();
+
+    llvm::StringRef new_mapping_from;
+    llvm::SmallString<256> new_mapping_to;
+
+    // Adding back any potentially reverse mapping stripped prefix.
+    // for new_mapping_to.
+    if (m_removed_prefix_opt.hasValue())
+      llvm::sys::path::append(new_mapping_to, m_removed_prefix_opt.getValue());
+
+    llvm::Optional<llvm::StringRef> new_mapping_from_opt =
+        check_suffix(sc_file_dir, request_file_dir, case_sensitive);
+    if (new_mapping_from_opt) {
+      new_mapping_from = new_mapping_from_opt.getValue();
+      if (new_mapping_to.empty())
+        new_mapping_to = ".";
+    } else {
+      llvm::Optional<llvm::StringRef> new_mapping_to_opt =
+          check_suffix(request_file_dir, sc_file_dir, case_sensitive);
+      if (new_mapping_to_opt) {
+        new_mapping_from = ".";
+        llvm::sys::path::append(new_mapping_to, new_mapping_to_opt.getValue());
+      }
+    }
+
+    if (!new_mapping_from.empty() && !new_mapping_to.empty()) {
+      LLDB_LOG(log, "generating auto source map from {0} to {1}",
+               new_mapping_from, new_mapping_to);
+      target.GetSourcePathMap().AppendUnique(new_mapping_from, new_mapping_to,
+                                             /*notify*/ true);
+    }
+  }
+}
+
 Searcher::CallbackReturn BreakpointResolverFileLine::SearchCallback(
     SearchFilter &filter, SymbolContext &context, Address *addr) {
   SymbolContextList sc_list;
 
   // There is a tricky bit here.  You can have two compilation units that
   // #include the same file, and in one of them the function at m_line_number
   // is used (and so code and a line entry for it is generated) but in the
   // other it isn't.  If we considered the CU's independently, then in the
if (cu_sp) {
       if (filter.CompUnitPasses(*cu_sp))
         cu_sp->ResolveSymbolContext(m_location_spec, eSymbolContextEverything,
                                     sc_list);
     }
   }
 
   FilterContexts(sc_list);
 
+  DeduceSourceMapping(sc_list);
+
   StreamString s;
   s.Printf("for %s:%d ",
            m_location_spec.GetFileSpec().GetFilename().AsCString("<Unknown>"),
            line);
 
   SetSCMatchesByLine(filter, sc_list, m_skip_prologue, s.GetString(), line,
                      column);
 

lldb/source/Target/PathMappingList.cpp

if (!rhs.m_pairs.empty()) {
     const_iterator pos, end = rhs.m_pairs.end();
     for (pos = rhs.m_pairs.begin(); pos != end; ++pos)
       m_pairs.push_back(*pos);
     if (notify && m_callback)
       m_callback(*this, m_callback_baton);
   }
 }
 
+void PathMappingList::AppendUnique(llvm::StringRef path,
+                                   llvm::StringRef replacement, bool notify) {
+  auto normalized_path = NormalizePath(path);
+  auto normalized_replacement = NormalizePath(replacement);
+  for (const auto &pair : m_pairs) {
+    if (pair.first.GetStringRef().equals(normalized_path) &&
+        pair.second.GetStringRef().equals(normalized_replacement))
+      return;
+  }
+  Append(path, replacement, notify);
+}
+
 void PathMappingList::Insert(llvm::StringRef path, llvm::StringRef replacement,
                              uint32_t index, bool notify) {
   ++m_mod_id;
   iterator insert_iter;
   if (index >= m_pairs.size())
     insert_iter = m_pairs.end();
   else
     insert_iter = m_pairs.begin() + index;
auto orig_style = FileSpec::GuessPathStyle(prefix).value_or(
         llvm::sys::path::Style::native);
     AppendPathComponents(remapped, path, orig_style);
     if (!only_if_exists || FileSystem::Instance().Exists(remapped))
       return remapped;
   }
   return {};
 }
 
-bool PathMappingList::ReverseRemapPath(const FileSpec &file, FileSpec &fixed) const {
+llvm::Optional<llvm::StringRef>
+PathMappingList::ReverseRemapPath(const FileSpec &file, FileSpec &fixed) const {
   std::string path = file.GetPath();
   llvm::StringRef path_ref(path);
   for (const auto &it : m_pairs) {
+    llvm::StringRef removed_prefix = it.second.GetStringRef();
     if (!path_ref.consume_front(it.second.GetStringRef()))
       continue;
     auto orig_file = it.first.GetStringRef();
-    auto orig_style = FileSpec::GuessPathStyle(orig_file).value_or(
+    auto orig_style = FileSpec::GuessPathStyle(orig_file).getValueOr(
         llvm::sys::path::Style::native);
     fixed.SetFile(orig_file, orig_style);
     AppendPathComponents(fixed, path_ref, orig_style);
-    return true;
+    return removed_prefix;
   }
-  return false;
+  return llvm::None;
 }
 
 llvm::Optional<FileSpec> PathMappingList::FindFile(const FileSpec &orig_spec) const {
   // We must normalize the orig_spec again using the host's path style,
   // otherwise there will be mismatch between the host and remote platform
   // if they use different path styles.
   if (auto remapped = RemapPath(NormalizePath(orig_spec.GetPath()),
                                 /*only_if_exists=*/true))

lldb/source/Target/Target.cpp

 BreakpointSP Target::CreateBreakpoint(const FileSpecList *containingModules,
                                       const FileSpec &file, uint32_t line_no,
                                       uint32_t column, lldb::addr_t offset,
                                       LazyBool check_inlines,
                                       LazyBool skip_prologue, bool internal,
                                       bool hardware,
                                       LazyBool move_to_nearest_code) {
   FileSpec remapped_file;
-  if (!GetSourcePathMap().ReverseRemapPath(file, remapped_file))
+  llvm::Optional<llvm::StringRef> removed_prefix_opt =
+      GetSourcePathMap().ReverseRemapPath(file, remapped_file);
+  if (!removed_prefix_opt)
     remapped_file = file;
 
   if (check_inlines == eLazyBoolCalculate) {
     const InlineStrategy inline_strategy = GetInlineStrategy();
     switch (inline_strategy) {
     case eInlineBreakpointsNever:
       check_inlines = eLazyBoolNo;
       break;
BreakpointSP Target::CreateBreakpoint(const FileSpecList *containingModules,
 
   SourceLocationSpec location_spec(remapped_file, line_no, column,
                                    check_inlines,
                                    !static_cast<bool>(move_to_nearest_code));
   if (!location_spec)
     return nullptr;
 
   BreakpointResolverSP resolver_sp(new BreakpointResolverFileLine(
-      nullptr, offset, skip_prologue, location_spec));
+      nullptr, offset, skip_prologue, location_spec, removed_prefix_opt));
   return CreateBreakpoint(filter_sp, resolver_sp, internal, hardware, true);
 }
 
 BreakpointSP Target::CreateBreakpoint(lldb::addr_t addr, bool internal,
                                       bool hardware) {
   Address so_addr;
 
   // Check for any reason we want to move this breakpoint to other address.
PathMappingList &TargetProperties::GetSourcePathMap() const {
   const uint32_t idx = ePropertySourceMap;
   OptionValuePathMappings *option_value =
       m_collection_sp->GetPropertyAtIndexAsOptionValuePathMappings(nullptr,
                                                                    false, idx);
   assert(option_value);
   return option_value->GetCurrentValue();
 }
 
+bool TargetProperties::GetAutoSourceMapRelative() const {
+  const uint32_t idx = ePropertyAutoSourceMapRelative;
+  return m_collection_sp->GetPropertyAtIndexAsBoolean(
+      nullptr, idx, g_target_properties[idx].default_uint_value != 0);
+}
+
 void TargetProperties::AppendExecutableSearchPaths(const FileSpec &dir) {
   const uint32_t idx = ePropertyExecutableSearchPaths;
   OptionValueFileSpecList *option_value =
       m_collection_sp->GetPropertyAtIndexAsOptionValueFileSpecList(nullptr,
                                                                    false, idx);
   assert(option_value);
   option_value->AppendCurrentValue(dir);
 }

lldb/source/Target/TargetProperties.td

def EnableSynthetic: Property<"enable-synthetic-value", "Boolean">,
     DefaultTrue,
     Desc<"Should synthetic values be used by default whenever available.">;
   def SkipPrologue: Property<"skip-prologue", "Boolean">,
     DefaultTrue,
     Desc<"Skip function prologues when setting breakpoints by name.">;
   def SourceMap: Property<"source-map", "PathMap">,
     DefaultStringValue<"">,
     Desc<"Source path remappings apply substitutions to the paths of source files, typically needed to debug from a different host than the one that built the target.  The source-map property consists of an array of pairs, the first element is a path prefix, and the second is its replacement.  The syntax is `prefix1 replacement1 prefix2 replacement2...`.  The pairs are checked in order, the first prefix that matches is used, and that prefix is substituted with the replacement.  A common pattern is to use source-map in conjunction with the clang -fdebug-prefix-map flag.  In the build, use `-fdebug-prefix-map=/path/to/build_dir=.` to rewrite the host specific build directory to `.`.  Then for debugging, use `settings set target.source-map . /path/to/local_dir` to convert `.` to a valid local path.">;
+  def AutoSourceMapRelative: Property<"auto-source-map-relative", "Boolean">,
+    DefaultTrue,
+    Desc<"Automatically deduce source path mappings based on source file breakpoint resolution. It only deduces source mapping if source file breakpoint request is using full path and if the debug info contains relative paths.">;
   def ExecutableSearchPaths: Property<"exec-search-paths", "FileSpecList">,
     DefaultStringValue<"">,
     Desc<"Executable search paths to use when locating executable files whose paths don't match the local file system.">;
   def DebugFileSearchPaths: Property<"debug-file-search-paths", "FileSpecList">,
     DefaultStringValue<"">,
     Desc<"List of directories to be searched when locating debug symbol files. See also symbols.enable-external-lookup.">;
   def ClangModuleSearchPaths: Property<"clang-module-search-paths", "FileSpecList">,
     DefaultStringValue<"">,

lldb/test/API/functionalities/breakpoint/breakpoint_command/TestBreakpointCommand.py

 """
 Test lldb breakpoint command add/list/delete.
 """
 
 
 
 import lldb
 from lldbsuite.test.decorators import *
 from lldbsuite.test.lldbtest import *
 from lldbsuite.test import lldbutil
+import json
 import os
 import side_effect
 
 
 
 class BreakpointCommandTestCase(TestBase):
 
     NO_DEBUG_INFO_TESTCASE = True
def test_breakpoints_with_relative_path_line_tables(self):
                 'Couldn\'t resolve breakpoint using full path "%s" in executate "%s" with '
                 'debug info that has relative path with matching suffix' % (path, self.getBuildArtifact("a.out")))
         invalid_paths = [
             "/x/b/c/main.cpp",
             "/x/c/main.cpp",
             "/x/main.cpp",
             "./x/y/a/d/c/main.cpp",
         ]
+        # Reset source map.
+        self.runCmd("settings clear target.source-map")
         for path in invalid_paths:
             bkpt = target.BreakpointCreateByLocation(path, 2)
             self.assertTrue(bkpt.GetNumLocations() == 0,
                 'Incorrectly resolved a breakpoint using full path "%s" with '
                 'debug info that has relative path with matching suffix' % (path))
 
 
     def setUp(self):
def test_breakpoint_delete_disabled(self):
         bp_1 = target.FindBreakpointByID(bp_id_1)
         self.assertFalse(bp_1.IsValid(), "Didn't delete disabled breakpoint 1")
 
         bp_2 = target.FindBreakpointByID(bp_id_2)
         self.assertTrue(bp_2.IsValid(), "Deleted enabled breakpoint 2")
 
         bp_3 = target.FindBreakpointByID(bp_id_3)
         self.assertFalse(bp_3.IsValid(), "Didn't delete disabled breakpoint 3")
+
+
+    def get_source_map_json(self):
+        stream = lldb.SBStream()
+        self.dbg.GetSetting("target.source-map").GetAsJSON(stream)
+        return json.loads(stream.GetData())
+
+    def verify_source_map_entry_pair(self, entry, original, replacement):
+        self.assertEquals(entry[0], original,
+            "source map entry 'original' does not match")
+        self.assertEquals(entry[1], replacement,
+            "source map entry 'replacement' does not match")
+
+    @skipIf(oslist=["windows"])
+    @no_debug_info_test
+    def test_breakpoints_auto_source_map_relative(self):
+        """
+            Test that with target.auto-source-map-relative settings.
+
+            The "relative.yaml" contains a line table that is:
+
+            Line table for a/b/c/main.cpp in `a.out
+            0x0000000100003f94: a/b/c/main.cpp:1
+            0x0000000100003fb0: a/b/c/main.cpp:2:3
+            0x0000000100003fb8: a/b/c/main.cpp:2:3
+        """
+        src_dir = self.getSourceDir()
+        yaml_path = os.path.join(src_dir, "relative.yaml")
+        yaml_base, ext = os.path.splitext(yaml_path)
+        obj_path = self.getBuildArtifact("a.out")
+        self.yaml2obj(yaml_path, obj_path)
+
+        # Create a target with the object file we just created from YAML
+        target = self.dbg.CreateTarget(obj_path)
+        # We now have debug information with line table paths that start are
+        # "./a/b/c/main.cpp".
+
+        source_map_json = self.get_source_map_json()
+        self.assertEquals(len(source_map_json), 0, "source map should be empty initially")
+
+        # Verify auto deduced source map when file path in debug info
+        # is a suffix of request breakpoint file path
+        path = "/x/y/a/b/c/main.cpp"
+        bp = target.BreakpointCreateByLocation(path, 2)
+        self.assertTrue(bp.GetNumLocations() > 0,
+                'Couldn\'t resolve breakpoint using full path "%s" in executate "%s" with '
+                'debug info that has relative path with matching suffix' % (path, self.getBuildArtifact("a.out")))
+
+        source_map_json = self.get_source_map_json()
+        self.assertEquals(len(source_map_json), 1, "source map should not be empty")
+        self.verify_source_map_entry_pair(source_map_json[0], ".", "/x/y")
+
+        # Reset source map.
+        self.runCmd("settings clear target.source-map")
+
+        # Verify source map will not auto deduced when file path of request breakpoint
+        # equals the file path in debug info.
+        path = "a/b/c/main.cpp"
+        bp = target.BreakpointCreateByLocation(path, 2)
+        self.assertTrue(bp.GetNumLocations() > 0,
+                'Couldn\'t resolve breakpoint using full path "%s" in executate "%s" with '
+                'debug info that has relative path with matching suffix' % (path, self.getBuildArtifact("a.out")))
+
+        source_map_json = self.get_source_map_json()
+        self.assertEquals(len(source_map_json), 0, "source map should not be deduced")

lldb/unittests/Target/PathMappingListTest.cpp

static void TestPathMappings(const PathMappingList &map,
   }
   for (const auto &match : matches) {
     SCOPED_TRACE(match.original.GetPath() + " -> " + match.remapped.GetPath());
     std::string orig_normalized = match.original.GetPath();
     EXPECT_TRUE(
         map.RemapPath(ConstString(match.original.GetPath()), actual_remapped));
     EXPECT_EQ(FileSpec(actual_remapped.GetStringRef()), match.remapped);
     FileSpec unmapped_spec;
-    EXPECT_TRUE(map.ReverseRemapPath(match.remapped, unmapped_spec));
+    EXPECT_TRUE(map.ReverseRemapPath(match.remapped, unmapped_spec).hasValue());
     std::string unmapped_path = unmapped_spec.GetPath();
     EXPECT_EQ(unmapped_path, orig_normalized);
   }
 }
 
 TEST(PathMappingListTest, RelativeTests) {
   Matches matches[] = {
     {".", "/tmp"},