Make clang-based tools find libc++ on MacOS

Summary:
When they read compiler args from compile_commands.json.
This change allows to run clang-based tools, like clang-tidy or clangd,
built from head using the compile_commands.json file produced for XCode
toolchains.

On MacOS clang can find the C++ standard library relative to the
compiler installation dir.

The logic to do this was based on resource dir as an approximation of
where the compiler is installed. This broke the tools that read
'compile_commands.json' and don't ship with the compiler, as they
typically change resource dir.

To workaround this, we now use compiler install dir detected by the driver
to better mimic the behavior of the original compiler when replaying the
compilations using other tools.

Reviewers: sammccall, arphaman, EricWF

Reviewed By: sammccall

Subscribers: ioeric, christof, kadircet, cfe-commits

Differential Revision: https://reviews.llvm.org/D54310

llvm-svn: 346652

1 files changed, 3 insertions, 8 deletions

diff --git a/clang/lib/Frontend/InitHeaderSearch.cpp b/clang/lib/Frontend/InitHeaderSearch.cpp
index deedb22f3e1..2f62ad3faf6 100644
--- a/clang/lib/Frontend/InitHeaderSearch.cpp
+++ b/clang/lib/Frontend/InitHeaderSearch.cpp
@@ -476,14 +476,9 @@ void InitHeaderSearch::AddDefaultIncludePaths(const LangOptions &Lang,
       if (triple.isOSDarwin()) {
         // On Darwin, libc++ may be installed alongside the compiler in
         // include/c++/v1.
-        if (!HSOpts.ResourceDir.empty()) {
-          // Remove version from foo/lib/clang/version
-          StringRef NoVer = llvm::sys::path::parent_path(HSOpts.ResourceDir);
-          // Remove clang from foo/lib/clang
-          StringRef Lib = llvm::sys::path::parent_path(NoVer);
-          // Remove lib from foo/lib
-          SmallString<128> P = llvm::sys::path::parent_path(Lib);
-
+        if (!HSOpts.InstallDir.empty()) {
+          // Get from foo/bin to foo.
+          SmallString<128> P(llvm::sys::path::parent_path(HSOpts.InstallDir));
           // Get foo/include/c++/v1
           llvm::sys::path::append(P, "include", "c++", "v1");
           AddUnmappedPath(P, CXXSystem, false);