[frontend] Don't include the C++ stdlib for -x assembler-with-cpp

The new C++ stdlib warning added in r335081 gets
triggered when compiling an assembly file with -x assembler-with-cpp.
This commit ensures that the C++ stdlib is not included when compiling assembly.
In general, it's not really useful to include the C++ stdlib search path when
compiling assembly source.

rdar://41359632

Differential Revision: https://reviews.llvm.org/D48736

llvm-svn: 335940

2 files changed, 7 insertions, 2 deletions

diff --git a/clang/lib/Frontend/InitHeaderSearch.cpp b/clang/lib/Frontend/InitHeaderSearch.cpp
index 85aeec461ba..8a70404629d 100644
--- a/clang/lib/Frontend/InitHeaderSearch.cpp
+++ b/clang/lib/Frontend/InitHeaderSearch.cpp
@@ -470,8 +470,8 @@ void InitHeaderSearch::AddDefaultIncludePaths(const LangOptions &Lang,
     break;
   }
 
-  if (Lang.CPlusPlus && HSOpts.UseStandardCXXIncludes &&
-      HSOpts.UseStandardSystemIncludes) {
+  if (Lang.CPlusPlus && !Lang.AsmPreprocessor &&
+      HSOpts.UseStandardCXXIncludes && HSOpts.UseStandardSystemIncludes) {
     if (HSOpts.UseLibcxx) {
       if (triple.isOSDarwin()) {
         // On Darwin, libc++ may be installed alongside the compiler in
diff --git a/clang/test/Frontend/nostdlib-for-asmpp.s b/clang/test/Frontend/nostdlib-for-asmpp.s
new file mode 100644
index 00000000000..330fee32a36
--- /dev/null
+++ b/clang/test/Frontend/nostdlib-for-asmpp.s
@@ -0,0 +1,5 @@
+// RUN: %clang -cc1 -x assembler-with-cpp -triple arm64-apple-ios6.0.0 -isysroot %S/doesnotexist -std=c++11 -v %s 2>&1 | FileCheck %s
+// The C++ stdlib path should not be included for an assembly source.
+
+// CHECK-NOT: usr/include/c++/
+// CHECK-NOT: include path for stdlibc++ headers not found; pass '-std=libc++' on the command line to use the libc++ standard library instead