Mark H Weaver <m...@netris.org> skribis: > This is clearly an issue with bdwgc on clang, and possibly only on > Apple's version of clang. Here's the relevant section of > gc/gc_config_macros.h from bdwgc 7.4.2: > > #ifndef GC_ATTR_ALLOC_SIZE > /* 'alloc_size' attribute improves __builtin_object_size correctness. */ > /* Only single-argument form of 'alloc_size' attribute is used. */ > # if defined(__GNUC__) && (__GNUC__ > 4 \ > || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3 && !defined(__ICC)) \ > || __clang_major__ > 3 \ > || (__clang_major__ == 3 && __clang_minor__ >= 2)) > # define GC_ATTR_ALLOC_SIZE(argnum) __attribute__((__alloc_size__(argnum))) > # else > # define GC_ATTR_ALLOC_SIZE(argnum) > # endif > #endif
AFAIK, Clang and ICC define __GNUC__ by default, even though they don’t implement all the features of the corresponding GCC, which may explain why the above doesn’t work as expected. > You can see that the bdwgc developers have made an effort to check both > GCC and clang version numbers before using the __alloc_size__ attribute. > The code above seems to suggest that they believed clang 3.2 or later > supported this attribute, whereas your version of clang seems to be > based on upstream clang 3.5. Perhaps Apple removed support for this > attribute from their clang? I think for Clang the right way would be to use the ‘__has_attribute’ magic macro: http://clang.llvm.org/docs/LanguageExtensions.html#has-attribute Ludo’.
