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Re: [PATCH 1/2] Add __clang_has_extension to sys/cdefs.h.

From: Florian Weimer <fweimer at redhat dot com>
To: Zack Weinberg <zackw at panix dot com>
Cc: GNU C Library <libc-alpha at sourceware dot org>
Date: Tue, 26 Apr 2016 15:48:23 +0200
Subject: Re: [PATCH 1/2] Add __clang_has_extension to sys/cdefs.h.
Authentication-results: sourceware.org; auth=none
References: <cover dot 1461444595 dot git dot zackw at panix dot com> <7d28608ab5396836526b235526e0b757236cfc85 dot 1461444595 dot git dot zackw at panix dot com> <571DC5D1 dot 5070209 at redhat dot com> <CAKCAbMjuZmKOMVBpPBHK06i5oherVeRhm4xswLrFAK3u-dsKkA at mail dot gmail dot com>

On 04/25/2016 03:57 PM, Zack Weinberg wrote:

Experimenting, clang treats __has_extension as an intrinsic *macro* --
for instance, #ifdef __has_extension is true.  So maybe we could just do

#ifndef __has_extension
#define __has_extension(...) 0
#endif

and that would be good enough?

This will confuse application that checks for the presence of__has_extension. glibc should not provide compiler-defined macroscoming from non-GNU compilers because it will be difficult to coordinatewith these parties (it's sometimes even difficult with GCC).


Florian

Follow-Ups:
- Re: [PATCH 1/2] Add __clang_has_extension to sys/cdefs.h.
  - From: Paul Eggert

References:
- [PATCH 0/2] Revised: deprecate sys/sysmacros.h inclusion from sys/types.h
  - From: Zack Weinberg
- [PATCH 1/2] Add __clang_has_extension to sys/cdefs.h.
  - From: Zack Weinberg
- Re: [PATCH 1/2] Add __clang_has_extension to sys/cdefs.h.
  - From: Florian Weimer
- Re: [PATCH 1/2] Add __clang_has_extension to sys/cdefs.h.
  - From: Zack Weinberg

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