Bug#1096266: 6tunnel: ftbfs with GCC-15

[Matthias Klose <doko@debian.org>]

Package: src:6tunnel
Version: 1:0.13-2
Severity: important
Tags: sid forky
User: debian-gcc@lists.debian.org
Usertags: ftbfs-gcc-15

[This bug is NOT targeted to the upcoming trixie release]

Please keep this issue open in the bug tracker for the package it
was filed for.  If a fix in another package is required, please
file a bug for the other package (or clone), and add a block in this
package. Please keep the issue open until the package can be built in
a follow-up test rebuild.

The package fails to build in a test rebuild on at least amd64 with
gcc-15/g++-15, but succeeds to build with gcc-14/g++-14. The
severity of this report will be raised before the forky release.

The full build log can be found at:
http://qa-logs.debian.net/2025/02/16/amd64exp/6tunnel_0.13-2_unstable_gccexp.log.gz
The last lines of the build log are at the end of this report.

To build with GCC 15, either set CC=gcc-15 CXX=g++-15 explicitly,
or install the gcc, g++, gfortran, ... packages from experimental.

  apt-get -t=experimental install g++ 

GCC 15 now defaults to the C23/C++23 standards, exposing many FTBFS.
Other Common build failures are new warnings resulting in build failures
with -Werror turned on, or new/dropped symbols in Debian symbols files.
For other C/C++ related build failures see the porting guide at
http://gcc.gnu.org/gcc-15/porting_to.html

[...]
/usr/include/signal.h:88:57: note: expected ‘__sighandler_t’ {aka ‘void (*)(int)’} but argument is of type ‘void (*)(void)’
   88 | extern __sighandler_t signal (int __sig, __sighandler_t __handler)
      |                                          ~~~~~~~~~~~~~~~^~~~~~~~~
6tunnel.c:560:6: note: ‘sighup’ declared here
  560 | void sighup()
      |      ^~~~~~
/usr/include/signal.h:72:16: note: ‘__sighandler_t’ declared here
   72 | typedef void (*__sighandler_t) (int);
      |                ^~~~~~~~~~~~~~
6tunnel.c:840:25: error: passing argument 2 of ‘signal’ from incompatible pointer type [-Wincompatible-pointer-types]
  840 |         signal(SIGCHLD, sigchld);
      |                         ^~~~~~~
      |                         |
      |                         void (*)(void)
/usr/include/signal.h:88:57: note: expected ‘__sighandler_t’ {aka ‘void (*)(int)’} but argument is of type ‘void (*)(void)’
   88 | extern __sighandler_t signal (int __sig, __sighandler_t __handler)
      |                                          ~~~~~~~~~~~~~~~^~~~~~~~~
6tunnel.c:568:6: note: ‘sigchld’ declared here
  568 | void sigchld()
      |      ^~~~~~~
/usr/include/signal.h:72:16: note: ‘__sighandler_t’ declared here
   72 | typedef void (*__sighandler_t) (int);
      |                ^~~~~~~~~~~~~~
6tunnel.c:841:25: error: passing argument 2 of ‘signal’ from incompatible pointer type [-Wincompatible-pointer-types]
  841 |         signal(SIGTERM, sigterm);
      |                         ^~~~~~~
      |                         |
      |                         void (*)(void)
/usr/include/signal.h:88:57: note: expected ‘__sighandler_t’ {aka ‘void (*)(int)’} but argument is of type ‘void (*)(void)’
   88 | extern __sighandler_t signal (int __sig, __sighandler_t __handler)
      |                                          ~~~~~~~~~~~~~~~^~~~~~~~~
6tunnel.c:578:6: note: ‘sigterm’ declared here
  578 | void sigterm()
      |      ^~~~~~~
/usr/include/signal.h:72:16: note: ‘__sighandler_t’ declared here
   72 | typedef void (*__sighandler_t) (int);
      |                ^~~~~~~~~~~~~~
6tunnel.c:842:24: error: passing argument 2 of ‘signal’ from incompatible pointer type [-Wincompatible-pointer-types]
  842 |         signal(SIGINT, sigterm);
      |                        ^~~~~~~
      |                        |
      |                        void (*)(void)
/usr/include/signal.h:88:57: note: expected ‘__sighandler_t’ {aka ‘void (*)(int)’} but argument is of type ‘void (*)(void)’
   88 | extern __sighandler_t signal (int __sig, __sighandler_t __handler)
      |                                          ~~~~~~~~~~~~~~~^~~~~~~~~
6tunnel.c:578:6: note: ‘sigterm’ declared here
  578 | void sigterm()
      |      ^~~~~~~
/usr/include/signal.h:72:16: note: ‘__sighandler_t’ declared here
   72 | typedef void (*__sighandler_t) (int);
      |                ^~~~~~~~~~~~~~
6tunnel.c:843:24: error: passing argument 2 of ‘signal’ from incompatible pointer type [-Wincompatible-pointer-types]
  843 |         signal(SIGHUP, sighup);
      |                        ^~~~~~
      |                        |
      |                        void (*)(void)
/usr/include/signal.h:88:57: note: expected ‘__sighandler_t’ {aka ‘void (*)(int)’} but argument is of type ‘void (*)(void)’
   88 | extern __sighandler_t signal (int __sig, __sighandler_t __handler)
      |                                          ~~~~~~~~~~~~~~~^~~~~~~~~
6tunnel.c:560:6: note: ‘sighup’ declared here
  560 | void sighup()
      |      ^~~~~~
/usr/include/signal.h:72:16: note: ‘__sighandler_t’ declared here
   72 | typedef void (*__sighandler_t) (int);
      |                ^~~~~~~~~~~~~~
make[1]: *** [Makefile:599: 6tunnel.o] Error 1
make[1]: Leaving directory '/build/reproducible-path/6tunnel-0.13'
dh_auto_build: error: make -j8 returned exit code 2
make: *** [debian/rules:7: binary] Error 25
dpkg-buildpackage: error: debian/rules binary subprocess returned exit status 2