[cfe-dev] [PATCH] libstdc++: Support std::is_aggregate on clang++ (was clang++: std::is_aggregate unusable with clang-5.0/libstdc++-7)

[Katsuhiko Nishimra via cfe-dev]

>From 56c4a18d0d8c8ce7aa1239880138775e4db06645 Mon Sep 17 00:00:00 2001
From: Katsuhiko Nishimra <ktns.87 at gmail.com>
Date: Thu, 27 Jul 2017 16:03:54 +0900
Subject: [PATCH] libstdc++: Support std::is_aggregate on clang++

Currently, libstdc++ tries to detect __is_aggregate built-in macro using
__has_builtin, but this fails on clang++ because __has_builtin on
clang++ detects only built-in functions, not built-in macros. This patch
adds a test using __is_identifier. Tested on clang++
5.0.0-svn308422-1~exp1 and g++ 7.1.0-10 from Debian unstable.
---
 libstdc++-v3/include/std/type_traits | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 390b6f40a..e7ec402fb 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -2894,6 +2894,11 @@ template <typename _From, typename _To>
 
 #if __GNUC__ >= 7
 # define _GLIBCXX_HAVE_BUILTIN_IS_AGGREGATE 1
+#elif defined(__is_identifier)
+// For clang
+# if ! __is_identifier(__is_aggregate)
+#  define _GLIBCXX_HAVE_BUILTIN_IS_AGGREGATE 1
+# endif
 #elif defined __has_builtin
 // For non-GNU compilers:
 # if __has_builtin(__is_aggregate)
-- 
2.13.3