[Driver] Fix libcxx detection on Darwin with clang run as ./clang

Summary:
By using '..' instead of fs::parent_path.

The intention of the code was to go from 'path/to/clang/bin' to
'path/to/clang/include'. In most cases parent_path works, however it
would fail when clang is run as './clang'.

This was noticed in Chromium's bug tracker, see
https://bugs.chromium.org/p/chromium/issues/detail?id=919761

Reviewers: arphaman, thakis, EricWF

Reviewed By: arphaman, thakis

Subscribers: christof, cfe-commits

Differential Revision: https://reviews.llvm.org/D56446

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@350714 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 4 deletions

diff --git a/lib/Driver/ToolChains/Darwin.cpp b/lib/Driver/ToolChains/Darwin.cpp
index 4e306fd960..50ecd13e69 100644
--- a/lib/Driver/ToolChains/Darwin.cpp
+++ b/lib/Driver/ToolChains/Darwin.cpp
@@ -1752,10 +1752,11 @@ void DarwinClang::AddClangCXXStdlibIncludeArgs(
       break;
     // On Darwin, libc++ may be installed alongside the compiler in
     // include/c++/v1.
-    // Get from 'foo/bin' to 'foo'.
-    SmallString<128> P = llvm::sys::path::parent_path(InstallDir);
-    // Get to 'foo/include/c++/v1'.
-    llvm::sys::path::append(P, "include", "c++", "v1");
+    // Get from 'foo/bin' to 'foo/include/c++/v1'.
+    SmallString<128> P = InstallDir;
+    // Note that InstallDir can be relative, so we have to '..' and not
+    // parent_path.
+    llvm::sys::path::append(P, "..", "include", "c++", "v1");
     addSystemInclude(DriverArgs, CC1Args, P);
     break;
   }