https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108734
--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to David Edelsohn from comment #5) > __has_builtin() does not mean that the builtin is inlined. It only means > that GCC recognizes the builtin. That is how __has_builtin() is documented. > In 32 bit mode, GCC emits an external reference for the builtin: 8 byte > atomic requires libatomic library, which is not linked by default (and > shouldn't be). And this is consistent with e.g. __has_builtin(__builtin_strlen). The fact that GCC recognizes the token "__builtin_strlen" doesn't mean that you don't need an extern definition of strlen for cases where the built-in isn't inlined. It's just that for the atomic built-ins the name of the built-in is the same as the name of the extern function that might be used.
