jfb added a comment. In D79504#2023274 <https://reviews.llvm.org/D79504#2023274>, @rsmith wrote:
> Clang's `<stdatomic.h>` uses the builtin as follows: > > #define atomic_is_lock_free(obj) __c11_atomic_is_lock_free(sizeof(*(obj))) > > > ... which, combined with the builtin returning `int`, results in a call > having the wrong type. So there's definitely a bug *somewhere*. > > I think what happened here is: the return type of the GCC > `__atomic_is_lock_free` / `__atomic_always_lock_free` builtins was `int` in > GCC 4.6 and earlier, and changed to `_Bool` in GCC 4.7 and later. Clang's > implementation followed GCC's behavior at the time, so returned `int`, and > no-one noticed that GCC changed its behavior in version 4.7. So we still > provide the old GCC behavior. > > Then, when `__c11_atomic_is_lock_free` was added, it got an `int` return type > as (I think) a copy-paste error. The `__c11` builtins are intended to exactly > match the semantics of the C11 atomic functions, so this was always wrong. > > I think we should make this change, to all three affected builtin functions. This sounds sensible to me. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D79504/new/ https://reviews.llvm.org/D79504 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
