From: Joseph Myers <joseph@codesourcery.com>
To: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Cc: <libc-alpha@sourceware.org>
Subject: Re: [PATCH 1/5] misc: Sync cdefs.h with gnulib
Date: Wed, 13 Jan 2021 18:09:10 +0000 [thread overview]
Message-ID: <alpine.DEB.2.22.394.2101131759560.1278751@digraph.polyomino.org.uk> (raw)
In-Reply-To: <20210113165826.1014708-1-adhemerval.zanella@linaro.org>
On Wed, 13 Jan 2021, Adhemerval Zanella via Libc-alpha wrote:
> +#if defined __STDC_VERSION__ && 201710L < __STDC_VERSION__
> +# define __attribute_maybe_unused__ [[__maybe_unused__]]
I don't think that will work with GCC 9 -std=c2x or -std=gnu2x (support
for [[]] attributes was added in GCC 10). This macro isn't used at all in
glibc, what compilers and options are expected to be supported for it in
gnulib?
If you compare __STDC_VERSION__ with the version for the previous
standard, and intend to support compilers such as GCC 9 -std=gnu2x, you
need to deal with incomplete implementations using placeholder values
(202000L in this case). (You might have incomplete implementations even
comparing with the final value used for C23, but they're less likely to be
so incomplete.)
When you're supporting [[__maybe_unused__]] you might want to support it
for C++17 as well as C2x. Or is this macro in gnulib only intended to be
used in C code, not C++?
--
Joseph S. Myers
joseph@codesourcery.com
next prev parent reply other threads:[~2021-01-13 18:09 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-13 16:58 Adhemerval Zanella
2021-01-13 16:58 ` [PATCH 2/5] malloc: Sync dynarray " Adhemerval Zanella
2021-02-09 19:12 ` Adhemerval Zanella
2021-01-13 16:58 ` [PATCH v2 3/5] regex: remove alloca usage on regex set_regs Adhemerval Zanella
2021-02-09 19:12 ` Adhemerval Zanella
2021-01-13 16:58 ` [PATCH v2 4/5] regexec: remove alloca usage in build_trtable Adhemerval Zanella
2021-02-09 19:12 ` Adhemerval Zanella
2021-01-13 16:58 ` [PATCH v2 5/5] regex: stop using alloca Adhemerval Zanella
2021-02-09 19:12 ` Adhemerval Zanella
2021-01-13 18:09 ` Joseph Myers [this message]
2021-01-13 18:30 ` [PATCH 1/5] misc: Sync cdefs.h with gnulib Adhemerval Zanella
2021-02-09 14:07 ` Adhemerval Zanella
2021-01-13 19:19 ` Paul Eggert
2021-01-13 19:21 ` Adhemerval Zanella
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