From f6600b7524e2956fcaef32da7ee9c7eca508c004 Mon Sep 17 00:00:00 2001
From: Asiri Rathnayake <asiri.rathnayake@arm.com>
Date: Tue, 13 Sep 2016 09:32:32 +0000
Subject: [PATCH] [libcxx] Fix gcc builds.

Step around a gcc pre-processor defect which causes it to fail to
parse the __has_include macro check.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@281310 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/__threading_support | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/include/__threading_support b/include/__threading_support
index b36a52ec9..86dc8c7be 100644
--- a/include/__threading_support
+++ b/include/__threading_support
@@ -19,9 +19,20 @@
 
 #ifndef _LIBCPP_HAS_NO_THREADS
 
-#if defined(_LIBCPP_HAS_THREAD_API_EXTERNAL) && (!defined(__has_include) || __has_include(<__external_threading>))
+// These checks are carefully arranged so as not to trigger a gcc pre-processor
+// defect which causes it to fail to parse the __has_include check below, the
+// redundancy is intentional.
+#if defined(_LIBCPP_HAS_THREAD_API_EXTERNAL)
+#if !defined(__clang__) && (_GNUC_VER < 500)
 #include <__external_threading>
-#else
+#define _LIBCPP_EXTERNAL_THREADING
+#elif !defined(__has_include) || __has_include(<__external_threading>)
+#include <__external_threading>
+#define _LIBCPP_EXTERNAL_THREADING
+#endif
+#endif
+
+#if !defined(_LIBCPP_EXTERNAL_THREADING)
 #include <pthread.h>
 #include <sched.h>
 #endif