[PATCH] Headers: Provide an ABI compatible max_align_t when _MSC_VER is defined

[David Majnemer]

Hi chandlerc, rsmith, rnk,

Our usual definition of max_align_t wouldn't match up with MSVC if it
was used in a template argument.

http://llvm-reviews.chandlerc.com/D2924

Files:
  lib/Headers/stddef.h
  test/Headers/c11.c

Index: lib/Headers/stddef.h
===================================================================
--- lib/Headers/stddef.h
+++ lib/Headers/stddef.h
@@ -85,12 +85,16 @@
 #endif
 
 #if __STDC_VERSION__ >= 201112L || __cplusplus >= 201103L
+#ifndef _MSC_VER
 typedef struct {
   long long __clang_max_align_nonce1
       __attribute__((__aligned__(__alignof__(long long))));
   long double __clang_max_align_nonce2
       __attribute__((__aligned__(__alignof__(long double))));
 } max_align_t;
+#else
+typedef double max_align_t;
+#endif
 #define __CLANG_MAX_ALIGN_T_DEFINED
 #endif
 
Index: test/Headers/c11.c
===================================================================
--- test/Headers/c11.c
+++ test/Headers/c11.c
@@ -1,6 +1,7 @@
 // RUN: %clang_cc1 -fsyntax-only -verify -std=c11 %s
 // RUN: %clang_cc1 -fsyntax-only -verify -std=c11 -fmodules %s
 // RUN: %clang_cc1 -fsyntax-only -verify -std=c11 -ffreestanding %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c11 -triple i686-pc-win32 -fmsc-version=1700 %s
 
 noreturn int f(); // expected-error 1+{{}}
 
@@ -27,6 +28,10 @@
 _Static_assert(sizeof(max_align_t) >= sizeof(long double), "");
 _Static_assert(alignof(max_align_t) >= alignof(long double), "");
 
+#ifdef _MSC_VER
+_Static_assert(sizeof(max_align_t) == sizeof(double), "");
+#endif
+
 // If we are freestanding, then also check RSIZE_MAX (in a hosted implementation
 // we will use the host stdint.h, which may not yet have C11 support).
 #ifndef __STDC_HOSTED__
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