[clang-cl] Print /showIncludes to stderr, if used in combination with /E, /EP or /P

This replicates 'cl.exe' behavior and allows for both preprocessor output and
dependency information to be extraced with a single compiler invocation.

This is especially useful for compiler caching with tools like Mozilla's sccache.

See: https://github.com/mozilla/sccache/issues/246

Patch By: fxb

Differential Revision: https://reviews.llvm.org/D46394

llvm-svn: 331533

1 files changed, 11 insertions, 1 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index ddaa16477aa..94e3332fc4f 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1130,7 +1130,17 @@ static void ParseDependencyOutputArgs(DependencyOutputOptions &Opts,
   Opts.ShowHeaderIncludes = Args.hasArg(OPT_H);
   Opts.HeaderIncludeOutputFile = Args.getLastArgValue(OPT_header_include_file);
   Opts.AddMissingHeaderDeps = Args.hasArg(OPT_MG);
-  Opts.PrintShowIncludes = Args.hasArg(OPT_show_includes);
+  if (Args.hasArg(OPT_show_includes)) {
+    // Writing both /showIncludes and preprocessor output to stdout
+    // would produce interleaved output, so use stderr for /showIncludes.
+    // This behaves the same as cl.exe, when /E, /EP or /P are passed.
+    if (Args.hasArg(options::OPT_E) || Args.hasArg(options::OPT_P))
+      Opts.ShowIncludesDest = ShowIncludesDestination::Stderr;
+    else
+      Opts.ShowIncludesDest = ShowIncludesDestination::Stdout;
+  } else {
+    Opts.ShowIncludesDest = ShowIncludesDestination::None;
+  }
   Opts.DOTOutputFile = Args.getLastArgValue(OPT_dependency_dot);
   Opts.ModuleDependencyOutputDir =
       Args.getLastArgValue(OPT_module_dependency_dir);