[libcxx] r292866 - Merge r292833 - Manually force the use of __decltype in C++03 with Clang 3.4.

[Eric Fiselier via cfe-commits]

Author: ericwf
Date: Mon Jan 23 19:01:55 2017
New Revision: 292866

URL: http://llvm.org/viewvc/llvm-project?rev=292866&view=rev
Log:
Merge r292833 - Manually force the use of __decltype in C++03 with Clang 3.4.

This merges a version of r292833 since it didn't apply cleanly due to other
upstream changes. Original commit message below:

<string> uses `decltype` in a way incompatible with `__typeof__`.
This is problematic when compiling <string> with Clang 3.4 because
even though it provides `__decltype` libc++ still used `__typeof__`
because clang 3.4 doesn't provide __is_identifier which libc++
uses to detect __decltype.

Modified:
    libcxx/branches/release_40/include/__config

Modified: libcxx/branches/release_40/include/__config
URL: http://llvm.org/viewvc/llvm-project/libcxx/branches/release_40/include/__config?rev=292866&r1=292865&r2=292866&view=diff
==============================================================================
--- libcxx/branches/release_40/include/__config (original)
+++ libcxx/branches/release_40/include/__config Mon Jan 23 19:01:55 2017
@@ -103,6 +103,9 @@
 
 #if defined(__clang__)
 #define _LIBCPP_COMPILER_CLANG
+# ifndef __apple_build_version__
+#   define _LIBCPP_CLANG_VER (__clang_major__ * 100 + __clang_minor__)
+# endif
 #elif defined(__GNUC__)
 #define _LIBCPP_COMPILER_GCC
 #elif defined(_MSC_VER)
@@ -111,6 +114,10 @@
 #define _LIBCPP_COMPILER_IBM
 #endif
 
+#ifndef _LIBCPP_CLANG_VER
+# define _LIBCPP_CLANG_VER 0
+#endif
+
 // FIXME: ABI detection should be done via compiler builtin macros. This
 // is just a placeholder until Clang implements such macros. For now assume
 // that Windows compilers pretending to be MSVC++ target the microsoft ABI.
@@ -741,7 +748,7 @@ template <unsigned> struct __static_asse
 
 #ifdef _LIBCPP_HAS_NO_DECLTYPE
 // GCC 4.6 provides __decltype in all standard modes.
-#if !__is_identifier(__decltype) || _GNUC_VER >= 406
+#if !__is_identifier(__decltype) || _LIBCPP_CLANG_VER >= 304 || _GNUC_VER >= 406
 #  define decltype(__x) __decltype(__x)
 #else
 #  define decltype(__x) __typeof__(__x)