On Fri, 17 Sep 2021, Richard Biener via Gcc wrote: > when the libc version targeted does not provide __memcmpeq? Or would > glibc through <string.h> magically communicate the availability of the new ABI > without actually declaring the function? > (I'm not sure whether a GCC build-time decision via configure is the > very best idea)
I was supposing a build-time decision (using GCC_GLIBC_VERSION_GTE_IFELSE to know if the glibc version on the target definitely has this function). But if we add a header declaration, you could check for __memcmpeq being declared (and so cover arbitrary C libraries, not just glibc, and avoid issues of needing to disable this logic for freestanding compilations, which would otherwise be an issue if a glibc-target toolchain is used for a freestanding kernel compilation). The case of people calling __builtin_memcmp (or declaring memcmp themselves) without string.h included probably isn't one it's important to optimize. -- Joseph S. Myers jos...@codesourcery.com
