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Message-ID: <b37138f6-cb88-cff3-e3e1-a71d94dbefef@disroot.org>
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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