libfile-mmagic-xs-perl: ftbfs with GCC-15

[gregoa]

We have the following bug reported to the Debian package of
File-MMagic-XS, c.f. https://bugs.debian.org/1097185

It doesn't seem to be a bug in the packaging, so you may want to take
a look. Thanks!

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Package: src:libfile-mmagic-xs-perl
Version: 0.09008-4
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/libfile-mmagic-xs-perl_0.09008-4_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

[...]
      |                                       ~^~~~~~~~~~~~~~~~~~~~~~ ~~~
src/MMagicST.c:456:36: note: in expansion of macro �EQUAL�
  456 |         if ((ptr->key != never) && EQUAL(table, ptr->key, *key)) {
      |                                    ^~~~~
src/MMagicST.h:15:11: note: declared here
   15 |     int (*compare)();
      |           ^~~~~~~
src/MMagicST.c: In function �delete_never�:
src/MMagicST.c:469:1: warning: old-style function definition [-Wold-style-definition]
  469 | delete_never(key, value, never)
      | ^~~~~~~~~~~~
src/MMagicST.c:470:15: warning: unused parameter �key� [-Wunused-parameter]
  470 |     st_data_t key, value, never;
      |               ^~~
src/MMagicST.c: In function �st_cleanup_safe�:
src/MMagicST.c:477:1: warning: old-style function definition [-Wold-style-definition]
  477 | st_cleanup_safe(table, never)
      | ^~~~~~~~~~~~~~~
src/MMagicST.c: In function �st_foreach�:
src/MMagicST.c:488:1: warning: old-style function definition [-Wold-style-definition]
  488 | st_foreach(table, func, arg)
      | ^~~~~~~~~~
src/MMagicST.c:500:23: error: too many arguments to function �func�; expected 0, have 4
  500 |             retval = (*func)(ptr->key, ptr->record, arg, 0);
      |                      ~^~~~~~ ~~~~~~~~
src/MMagicST.c:511:31: error: too many arguments to function �func�; expected 0, have 4
  511 |                     retval = (*func)(0, 0, arg, 1);
      |                              ~^~~~~~ ~
src/MMagicST.c: In function �strhash�:
src/MMagicST.c:538:1: warning: old-style function definition [-Wold-style-definition]
  538 | strhash(string)
      | ^~~~~~~
src/MMagicST.c: In function �numcmp�:
src/MMagicST.c:577:1: warning: old-style function definition [-Wold-style-definition]
  577 | numcmp(x, y)
      | ^~~~~~
src/MMagicST.c: In function �numhash�:
src/MMagicST.c:584:1: warning: old-style function definition [-Wold-style-definition]
  584 | numhash(n)
      | ^~~~~~~
make[1]: *** [Makefile:354: src/MMagicST.o] Error 1
make[1]: *** Waiting for unfinished jobs....
mv src/MMagic.xsc src/MMagic.c
src/perl-mmagic-xs.c: In function �PerlFMM_ascmagic�:
src/perl-mmagic-xs.c:1645:36: warning: pointer targets in passing argument 1 of �strlen� differ in signedness [-Wpointer-sign]
 1645 |     rc = fmm_ascmagic(data, strlen(data), &type);
      |                                    ^~~~
      |                                    |
      |                                    unsigned char *
In file included from /usr/lib/x86_64-linux-gnu/perl/5.40/CORE/perl.h:1711,
                 from src/perl-mmagic-xs.h:5,
                 from src/perl-mmagic-xs.c:105:
/usr/include/string.h:407:35: note: expected �const char *� but argument is of type �unsigned char *�
  407 | extern size_t strlen (const char *__s)
      |                       ~~~~~~~~~~~~^~~
src/perl-mmagic-xs.c: In function �fmm_append_buf�:
src/perl-mmagic-xs.c:375:5: warning: �__builtin_strncat� specified bound depends on the length of the source argument [-Wstringop-overflow=]
  375 |     strncat(*dst, buf, strlen(buf));
      |     ^
src/perl-mmagic-xs.c:367:9: note: length computed here
  367 |     if (strlen(buf) + 1 > MAXMIMESTRING - strlen(*dst)) {
      |         ^~~~~~~~~~~
src/perl-mmagic-xs.c: In function �fmm_ext_magic�:
src/perl-mmagic-xs.c:1457:5: warning: �__builtin_strncpy� specified bound 8192 equals destination size [-Wstringop-truncation]
 1457 |     strncpy(ext, dot + 1, BUFSIZ);
      |     ^
make[1]: Leaving directory '/build/reproducible-path/libfile-mmagic-xs-perl-0.09008'
dh_auto_build: error: make -j8 returned exit code 2
make: *** [debian/rules:13: binary] Error 25
dpkg-buildpackage: error: debian/rules binary subprocess returned exit status 2

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Thanks for considering,
gregor herrmann,
Debian Perl Group