On Fri, Nov 13, 2015 at 09:58:30PM +0100, Bernd Schmidt wrote: > On 11/13/2015 06:11 PM, Szabolcs Nagy wrote: > >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. > > > #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"); > > Can't say I like the __asm__ after the #if/#else/#endif block.
It could trivially be moved inside. > > 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; > > Random observation: this seems overly conservative as malloc is > defined to return something aligned to more than one byte. You can assume it returns memory aligned to _Alignof(max_align_t), nothing more. But on some broken library implementations (windows?) you might not even get that. > Couldn't this bug be fixed by either > - just overallocating and aligning manually (eliminating the dependence > entirely) I don't think so; then the memory is not freeable, at least not without extra hacks. > - or moving _mm_malloc into libgcc.a? I wouldn't oppose that, but it seems like a more invasive change than is necessary to fix this bug. Rich
