[Pkg-swan-devel] Bug#1147712: strongswan: FTBFS with GCC 16: custom printf specifier %B rejected because -Wno-format is overridden

[Paul Menzel]

Dear Santiago,


Thank you for your immediate reply.

Am 14.09.26 um 17:09 schrieb Santiago Vila:

> On Mon, Sep 14, 2026 at 04:48:40PM +0200, Paul Menzel wrote:

[…]

>> AI disclaimer: Analyzed and drafted by claude-opus-5, and reviewed and
>> edited by me.
>>
>> Building strongswan with `debuild -us -uc -b` on Debian sid/unstable
>> with *gcc* 4:16.1.0-3 fails:
> 
> [ Please note that the relevant version here would be the one in the
>    package called "gcc-16", not "gcc", which is just the package
>    containing the symlinkg gcc -> the-real-gcc ].

It’s *gcc-16* 16.2.0-2.

> I'm attaching my build log, made a few minutes ago on current unstable.
> 
> If you can still reproduce the build failure on current unstable
> please try building with sbuild and diff your build log with mine.
claude-opus-5 found it. Upstream’s configure behaves differently, when a 
directory `.git` is present, and adds `-Werror`. configure.ac:516:

     # enable warnings and -Werror by default when building from the 
repo (check with
     # -e as .git is a file in worktrees)
     if test x$warnings_given = xfalse -a -e "$srcdir"/.git; then
           warnings=true
     fi

then configure.ac:1401-1425:

     WARN_CFLAGS=
     if test x$warnings = xtrue; then
           WARN_CFLAGS="-Werror -Wall -Wextra"     # ← only when .git exists
     fi
     WARN_CFLAGS="$WARN_CFLAGS -Wno-format"      # ← the suppression 
lands *after* -Werror
     WARN_CFLAGS="$WARN_CFLAGS -Wno-format-security"
     [...]
     CFLAGS="$WARN_CFLAGS $CFLAGS"               # ← hardening's 
-Wformat lands last and wins

`debcheckout` gives you a git tree; the buildds unpack a .dsc. That 
single difference decides error vs. warning.

The warnings are also present in your log. No idea, how to proceed.


Kind regards,

Paul