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Message-ID: <1aaa9a0f-8425-4c48-8698-65a3765a67a2@cs.ucla.edu>
Date: Fri, 20 Jun 2025 18:34:25 -0700
From: Paul Eggert <eggert@...ucla.edu>
To: Alejandro Colomar <alx@...nel.org>, Thorsten Glaser <tg@...bsd.de>
Cc: libc-alpha@...rceware.org, bug-gnulib@....org, musl@...ts.openwall.com,
наб <nabijaczleweli@...ijaczleweli.xyz>,
Douglas McIlroy <douglas.mcilroy@...tmouth.edu>,
Robert Seacord <rcseacord@...il.com>, Elliott Hughes <enh@...gle.com>,
Bruno Haible <bruno@...sp.org>, JeanHeyd Meneide <phdofthehouse@...il.com>,
Rich Felker <dalias@...c.org>,
Adhemerval Zanella Netto <adhemerval.zanella@...aro.org>,
Joseph Myers <josmyers@...hat.com>, Florian Weimer <fweimer@...hat.com>,
Laurent Bercot <ska-dietlibc@...rnet.org>, Andreas Schwab <schwab@...e.de>,
Eric Blake <eblake@...hat.com>, Vincent Lefevre <vincent@...c17.net>,
Mark Harris <mark.hsj@...il.com>, Collin Funk <collin.funk1@...il.com>,
Wilco Dijkstra <Wilco.Dijkstra@....com>, DJ Delorie <dj@...hat.com>,
Cristian Rodríguez <cristian@...riguez.im>,
Siddhesh Poyarekar <siddhesh@...plt.org>, Sam James <sam@...too.org>,
Mark Wielaard <mark@...mp.org>, "Maciej W. Rozycki" <macro@...hat.com>,
Martin Uecker <ma.uecker@...il.com>,
Christopher Bazley <chris.bazley.wg14@...il.com>, eskil@...ession.se
Subject: Re: alx-0029r1 - Restore the traditional realloc(3) specification
On 2025-06-20 18:06, Alejandro Colomar wrote:
> + to both return a null pointer and set errno to ENOMEM.
Given the proposed change, I don't see why ENOMEM must be added to the C
spec. The spec changes malloc and realloc so that returning null means
failure (i.e., out of memory) and returning non-null means success. In
that case, there seems to be no pressing need for ENOMEM in the C
standard (as opposed to POSIX).
If ENOMEM is really needed, its presence should be justified in the
proposal. Alternatively, the proposal could be divided into two: the
main proposal is the null-if-and-only-if-failure part, and ENOMEM could
be the secondary proposal.
One other thing: Doug McIlroy's point was that realloc(p,n) should never
fail when p already addresses storage of size n or greater. As a
corollary, realloc(p,0) should never fail when p is non-null. It might
be helpful to add this as a third proposal. A lot of apps already assume
McIlroy's point, after all.
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