[PATCH, x86] Fix posix_memalign declaration in mm_malloc.h

[Szabolcs Nagy]

Followup to https://gcc.gnu.org/ml/gcc-patches/2015-05/msg01433.html

The posix_memalign declaration is incompatible with musl libc in C++,
because of the exception specification (matters with -std=c++11
-pedantic-errors).  It also pollutes the namespace and lacks protection
against a potential macro definition that is allowed by POSIX.  The
fix avoids source level namespace pollution but retains the dependency
on the posix_memalign extern libc symbol.

Added a test case for the namespace issue.

OK for trunk?

gcc/ChangeLog:

2015-11-13  Szabolcs Nagy  <szabolcs.n...@arm.com>

        * config/i386/pmm_malloc.h (posix_memalign): Renamed to ...
        (_mm_posix_memalign): This.  Use posix_memalign as extern
        symbol only.

gcc/testsuite/ChangeLog:

2015-11-13  Szabolcs Nagy  <szabolcs.n...@arm.com>

        * g++.dg/other/mm_malloc.C: New.

diff --git a/gcc/config/i386/pmm_malloc.h b/gcc/config/i386/pmm_malloc.h
index 901001b..0696c20 100644
--- a/gcc/config/i386/pmm_malloc.h
+++ b/gcc/config/i386/pmm_malloc.h
@@ -27,12 +27,13 @@
 #include <stdlib.h>
 
 /* We can't depend on <stdlib.h> since the prototype of posix_memalign
-   may not be visible.  */
+   may not be visible and we can't pollute the namespace either.  */
 #ifndef __cplusplus
-extern int posix_memalign (void **, size_t, size_t);
+extern int _mm_posix_memalign (void **, size_t, size_t)
 #else
-extern "C" int posix_memalign (void **, size_t, size_t) throw ();
+extern "C" int _mm_posix_memalign (void **, size_t, size_t) throw ()
 #endif
+__asm__("posix_memalign");
 
 static __inline void *
 _mm_malloc (size_t size, size_t alignment)
@@ -42,7 +43,7 @@ _mm_malloc (size_t size, size_t alignment)
     return malloc (size);
   if (alignment == 2 || (sizeof (void *) == 8 && alignment == 4))
     alignment = sizeof (void *);
-  if (posix_memalign (&ptr, alignment, size) == 0)
+  if (_mm_posix_memalign (&ptr, alignment, size) == 0)
     return ptr;
   else
     return NULL;
diff --git a/gcc/testsuite/g++.dg/other/mm_malloc.C b/gcc/testsuite/g++.dg/other/mm_malloc.C
new file mode 100644
index 0000000..00582cc
--- /dev/null
+++ b/gcc/testsuite/g++.dg/other/mm_malloc.C
@@ -0,0 +1,17 @@
+/* { dg-do compile { target i?86-*-* x86_64-*-* } } */
+/* { dg-options "-std=c++11" } */
+
+/* Suppress POSIX declarations in libc headers in standard C++ mode.  */
+#undef _GNU_SOURCE
+
+#define posix_memalign user_can_do_this
+
+#include <mm_malloc.h>
+
+void *
+foo ()
+{
+	return _mm_malloc (16, 16);
+}
+
+/* { dg-final { scan-assembler "call\\tposix_memalign" } } */