From: Sam James <sam@gentoo.org>
To: Andres Freund <andres@anarazel.de>
Cc: Tom Lane <tgl@sss.pgh.pa.us>,  Thomas Munro <thomas.munro@gmail.com>,
  tharakan@gmail.com,  Peter Eisentraut <peter@eisentraut.org>,
  pgsql-bugs@lists.postgresql.org
Subject: Re: Build failure with GCC 15 (defaults to -std=gnu23)
In-Reply-To: <eu34f6armrlbq7cdai3dy45576h3qybme47uxens4cowpghzqe@52owmagijfiu>
	(Andres Freund's message of "Wed, 27 Nov 2024 13:50:59 -0500")
Organization: Gentoo
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Date: Wed, 27 Nov 2024 19:01:36 +0000
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Andres Freund <andres@anarazel.de> writes:

> Hi,
>
> On 2024-11-27 13:28:24 -0500, Tom Lane wrote:
>> Thomas Munro <thomas.munro@gmail.com> writes:
>> > Pushed.  Alligator is turning green in the back branches, only one more to go.
>> > I see that Peter also pushed the reserved word patches.  Apparently
>> > that gcc bug it's blowing up on might go away with -g0 (see link
>> > earlier), but anyway it's a nightly build compiler so fingers crossed
>> > for a fix soon.  The newer branches are building and running for me on
>> > { gcc14, gcc15, clang18 } -std=gnu23, and apparently the bug was even
>> > in gcc14, so it must require some unlikely conditions that alligator
>> > has stumbled on.
>> 
>> Looks like flaviventris and serinus just updated to the same broken
>> compiler version that alligator is using :-(.  Maybe we'd better
>> file a formal bug report?
>
> I run a development gcc locally, and I just had updated it this morning
> (4a868591169). Interestingly I don't see the ICE with it.
>
> But I can reproduce it with debian sid's gcc-snapshot, with exactly the same
> compiler arguments. The snapshot's version:
>      gcc (Debian 20241123-1) 15.0.0 20241123 (experimental) [master r15-5606-g4aa4162e365]
>
> so it looks like the bug might have been fixed recently?
>
> I'm not sure this is really the bug linked to earlier [1]. I can't repro the
> issue with 14, for example.
>
> It's possible it requires specific gcc configure flags to be triggered?
>
> Luckily -g1 does, at least locally, work around the issue with
> gcc-snapshot. So I guess I'll make flaviventris and serinus use that for now
> :/
>
> Greetings,
>
> Andres Freund
>
> [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113688

See https://gcc.gnu.org/PR117724 as well. The issues are related in that
canonicalisation of struct types keeps needing revisiting, more so in
light of C23 changes.

Note also that the ICE is only with "checking" (~assertions) which is
enabled at a stricter level for non-releases by default, so some of it
may affect 14 but not show up there.

Martin Uecker has posted a patch which is currently being reviewed. I
wouldn't worry about it until that lands unless the build failures continue.

thanks,
sam