From: David Bremner <david@tethera.net>
To: Michael J Gruber <michaeljgruber+grubix+git@gmail.com>
Subject: Re: compilation issues with gcc-15 / gcc-16
In-Reply-To: <CAA19uiR+u2p4FpjA-Ub=dBKLGSVtULBMPs3F9i4dWwRcG12yhA@mail.gmail.com>
References: <87pl3e2nvl.fsf@tethera.net>
 <CAA19uiR+u2p4FpjA-Ub=dBKLGSVtULBMPs3F9i4dWwRcG12yhA@mail.gmail.com>
Date: Tue, 05 May 2026 21:20:14 +0900
Message-ID: <87lddy120x.fsf@tethera.net>
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Michael J Gruber <michaeljgruber+grubix+git@gmail.com> writes:

> Am Sa., 2. Mai 2026 um 10:54 Uhr schrieb David Bremner <david@tethera.net>:
>>
>>
>> I'm not sure if this is a problem with notmuch and gcc becoming stricter
>> / more ambitious, or a compiler bug, but today I learned that gcc-15
>> 15.2.0-7 (an upstream snapshot) and gcc-16 both miscompile notmuch at
>> optimization level O2. A workaround seems to be to run configure as
>>
>> CFLAGS="-g -O1" ./configure
>>
>> I filed a Debian bug report at
>>
>>   https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1135526
>
> FYI:
> I don't see this on Fedora with notmuch 0.40 and gcc-16.0.1-0.11.fc44
> resp. gcc-15.2.1-7.fc43.
>
> CFLAGS='-O2 -flto=auto -ffat-lto-objects -fexceptions -g
> -grecord-gcc-switches -pipe -Wall -Werror=format-security
> -Wp,-U_FORTIFY_SOURCE,-D_FORTIFY_SOURCE=3 -Wp,-D_GLIBCXX_ASSERTIONS
> -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1
> -fstack-protector-strong -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1
>  -mbranch-protection=standard -fasynchronous-unwind-tables
> -fstack-clash-protection -fno-omit-frame-pointer
> -mno-omit-leaf-frame-pointer  '

Thanks for the update. It's particularly interesting that gcc-16 is
fine. I had assumed the problem was some patch cherry-picked from
gcc-16, but I guess it's more complicated than that.

d
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