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Message-ID: <24847552-e2ff-4cd7-ae12-f167f6fd822b@cs.ucla.edu>
Date: Sun, 9 Nov 2025 07:31:37 -0800
From: Paul Eggert <eggert@...ucla.edu>
To: Alejandro Colomar <alx@...nel.org>
Cc: libc-alpha@...rceware.org, musl@...ts.openwall.com,
"A. Wilcox" <AWilcox@...cox-tech.com>,
Lénárd Szolnoki <cpp@...ardszolnoki.com>,
Collin Funk <collin.funk1@...il.com>,
Arthur O'Dwyer <arthur.j.odwyer@...il.com>,
Jonathan Wakely <jwakely@...hat.com>, "Paul E. McKenney"
<paulmck@...nel.org>, Thiago Macieira <thiago@...ieira.org>
Subject: Re: Re: realloci(): A realloc() variant that works in-place
On 2025-11-09 03:37, Alejandro Colomar wrote:
>>> That would make sanitizers and static analyzers unable to verify lots of
>>> code
>> No, just the opposite. Currently sanitizers etc. spend useless work checking
>> for C23 rules that don't correspond to any hardware or correctness needs;
>> they're simply rules imposed by the C committee. This checking is
>> counterproductive to real-world software development.
> I'm worried that it might decrease the ability of static analyzers to
> detect memory leaks. Currently, a static analyzer (such as GCC's
> -fanalyzer) can see calls to [[gnu::malloc(realloc, 1)]] functions and
> assume that realloc(3) free's them. If realloc(3) would only free(3)
> conditionally, then you couldn't apply that attribute, which would make
> analysis more difficult.
Again, this is backwards. If the spec for P=realloc(Q,R) is changed so
that it's valid to check P==Q afterwards (which it is on every practical
production platform), then static analyzers can and should be changed
accordingly. The P==Q situation will not count as a memory leak, and
other situations will still count. This will be an improvement over the
current situation, where static analyzers issue false alarms about such
code.
Static analyzers should be our servants, not our masters.
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