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Message-ID: <20250619123613.GC2742@qaa.vinc17.org>
Date: Thu, 19 Jun 2025 14:36:13 +0200
From: Vincent Lefevre <vincent@...c17.net>
To: Alejandro Colomar <alx@...nel.org>
Cc: Rich Felker <dalias@...c.org>, linux-man@...r.kernel.org,
musl@...ts.openwall.com, libc-alpha@...rceware.org,
Paul Eggert <eggert@...ucla.edu>, Bruno Haible <bruno@...sp.org>,
bug-gnulib@....org
Subject: Re: malloc.3: Clarify realloc(3) standards conformance
On 2025-06-19 12:54:52 +0200, Alejandro Colomar wrote:
> +BUGS
> + Programmers would naturally expect that realloc(p, n) is consis‐
> + tent with free(p) and malloc(n). This is not explicitly re‐
> + quired by POSIX.1‐2024, but all conforming implementations are
> + consistent with that.
> +
> + The glibc implementation of realloc() is not consistent with
> + that, and as a consequence, it is dangerous to call
> + realloc(p, 0) in glibc.
> +
> + A trivial workaround for glibc is calling it as
> + realloc(p, n?:1).
n?:1 is a GNU extension:
warning: ISO C forbids omitting the middle term of a ‘?:’ expression [-Wpedantic]
with gcc -pedantic -std=c23, and such code should not be given in
examples (as a workaround should still be valid for portable code).
--
Vincent Lefèvre <vincent@...c17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / Pascaline project (LIP, ENS-Lyon)
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