[clang] Add the flag -ffile-reproducible

When Clang generates the path prefix (i.e. the path of the directory
where the file is) when generating FILE, __builtin_FILE(), and
std::source_location, Clang uses the platform-specific path separator
character of the build environment where Clang _itself_ is built. This
leads to inconsistencies in Chrome builds where Clang running on
non-Windows environments uses the forward slash (/) path separator
while Clang running on Windows builds uses the backslash (\) path
separator. To fix this, we add a flag -ffile-reproducible (and its
inverse, -fno-file-reproducible) to have Clang use the target's
platform-specific file separator character.

Additionally, the existing flags -fmacro-prefix-map and
-ffile-prefix-map now both imply -ffile-reproducible. This can be
overriden by setting -fno-file-reproducible.

[0]: https://crbug.com/1310767

Differential revision: https://reviews.llvm.org/D122766

1 files changed, 11 insertions, 0 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 2e205f34..88125da 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -3541,6 +3541,11 @@ void CompilerInvocation::GenerateLangArgs(const LangOptions &Opts,
   else
     GenerateArg(Args, OPT_fno_experimental_relative_cxx_abi_vtables, SA);
 
+  if (Opts.UseTargetPathSeparator)
+    GenerateArg(Args, OPT_ffile_reproducible, SA);
+  else
+    GenerateArg(Args, OPT_fno_file_reproducible, SA);
+
   for (const auto &MP : Opts.MacroPrefixMap)
     GenerateArg(Args, OPT_fmacro_prefix_map_EQ, MP.first + "=" + MP.second, SA);
 
@@ -4072,6 +4077,12 @@ bool CompilerInvocation::ParseLangArgs(LangOptions &Opts, ArgList &Args,
         {std::string(Split.first), std::string(Split.second)});
   }
 
+  Opts.UseTargetPathSeparator =
+      !Args.getLastArg(OPT_fno_file_reproducible) &&
+      (Args.getLastArg(OPT_ffile_compilation_dir_EQ) ||
+       Args.getLastArg(OPT_fmacro_prefix_map_EQ) ||
+       Args.getLastArg(OPT_ffile_reproducible));
+
   // Error if -mvscale-min is unbounded.
   if (Arg *A = Args.getLastArg(options::OPT_mvscale_min_EQ)) {
     unsigned VScaleMin;