#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_

[llvmbot]

Bugzilla Link	11174
Resolution	FIXED
Resolved on	Nov 05, 2015 13:43
Version	unspecified
OS	All
Blocks	llvm/llvm-bugzilla-archive#24345
Reporter	LLVM Bugzilla Contributor
CC	@Bigcheese,@weiguozhi,@echristo,@efriedma-quic,@rprichard

[llvmbot]

GCC rather helpfully defines these macros when it is capable of supporting atomic intrinsics for a particular word size. For example:

• on -march=i386 atomics are not supported
• on -march=i486 atomics are supported only for word sizes up to 4
• on -march=i586 and higher it's supported for 8 as well

clang doesn't define these macros and doesn't seem to define anything equivalent either. That prevents having an #ifdef around code that might either use these operations or elect to implement them with a mutex.

[llvmbot]

This is actually an ABI issue, and should be raised in priority. See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42734

[rprichard]

Also see http://llvm.org/bugs/show_bug.cgi?id=12730.

[weiguozhi]

I met the same problem when building glib. Since lack of __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4, it caused the glib configuration failed.

[Bigcheese]

Patch: http://llvm-reviews.chandlerc.com/D621

[Bigcheese]

Fixed in r178816 for x86.

[llvmbot]

mentioned in issue llvm/llvm-bugzilla-archive#24345