Date: Fri, 17 Sep 2021 14:19:53 +0000 From: Joseph Myers <joseph@...esourcery.com> To: Richard Biener <richard.guenther@...il.com> CC: GCC Development <gcc@....gnu.org>, GNU C Library <libc-alpha@...rceware.org>, <libc-coord@...ts.openwall.com> Subject: Re: Add new ABI '__memcmpeq()' to libc 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 joseph@...esourcery.com
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