Date: Fri, 16 Apr 2021 14:57:21 -0300 From: Érico Nogueira <ericonr@...root.org> To: Rich Felker <dalias@...c.org> Cc: musl@...ts.openwall.com Subject: Re: [PATCH 2/2] include <stdc-predef.h> in <features.h> Em 16/04/2021 11:26, Rich Felker escreveu: > On Thu, Apr 15, 2021 at 09:35:21PM -0300, Érico Nogueira wrote: >> GCC source code does contain a function to pre-include the >> <stdc-predef.h> header for glibc targets, but even so glibc still I seem to have been mistaken about the feature being glibc specific; using echo "" | cc -xc - -E it seems the file does end up being included automatically. However, when using clang instead of gcc, it isn't included automatically. I don't know if this is something that clang ought to fix, is there some sort of standard about <stdc-predef.h>? Michael Forney's cproc compiler doesn't seem to touch it either. >> includes it in their own <features.h> header. furthermore, even if GCC >> implemented this for musl targets, it is still necessary for other >> compilers or previous versions of GCC. >> --- >> include/features.h | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/include/features.h b/include/features.h >> index 85cfb72a..f3d53cbe 100644 >> --- a/include/features.h >> +++ b/include/features.h >> @@ -1,6 +1,8 @@ >> #ifndef _FEATURES_H >> #define _FEATURES_H >> >> +#include <stdc-predef.h> >> + >> #if defined(_ALL_SOURCE) && !defined(_GNU_SOURCE) >> #define _GNU_SOURCE 1 >> #endif >> -- >> 2.31.1 > > I've hesitated to do this because features.h is not consistently > included from all standard headers (only if it's needed), and the > result would be inconsistent exposure of these macros. (Also > inconsistent if they're checked before any standard headers are > included, which is unfixable.) I think it makes more sense to just add > "-include stdc-predef.h" to the compiler specfile or equivalent if it > doesn't auto-include it, so that you get behavior that actually > matches the spec. Do you know if clang can use the specfile? That would make it worth it adding the entry, since GCC has the expected behavior already. > > Rich >
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