Errors when compiling with '-Werror=discarded-qualifier'

[jorti]

Fedora builds with GCC 16 are using the option -Werror=discarded-qualifiers and the compilation fails with these errors:

/usr/bin/gcc -D_GNU_SOURCE  -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  -m32 -march=i686 -mtune=generic -msse2 -mfpmath=sse -mstackrealign -fasynchronous-unwind-tables -fstack-clash-protection -mtls-dialect=gnu -g3 -std=c99   -Os -Wall -Werror -pedantic -Wextra -Werror=implicit-function-declaration -Wformat -Werror=format-security -Werror=format-nonliteral -Wno-unused-parameter -Wmissing-declarations -MD -MT CMakeFiles/odhcp6c.dir/src/md5.c.o -MF CMakeFiles/odhcp6c.dir/src/md5.c.o.d -o CMakeFiles/odhcp6c.dir/src/md5.c.o -c /builddir/build/BUILD/odhcp6c-0-build/odhcp6c-96d9e0b6e81330c61c954c6bc73a2302276fcda1/src/md5.c
/builddir/build/BUILD/odhcp6c-0-build/odhcp6c-96d9e0b6e81330c61c954c6bc73a2302276fcda1/src/odhcp6c.c: In function ‘parse_opt_string’:
/builddir/build/BUILD/odhcp6c-0-build/odhcp6c-96d9e0b6e81330c61c954c6bc73a2302276fcda1/src/odhcp6c.c:1032:21: error: initialization discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
 1032 |         char *sep = strpbrk(src, ARRAY_SEP);
      |                     ^~~~~~~
/builddir/build/BUILD/odhcp6c-0-build/odhcp6c-96d9e0b6e81330c61c954c6bc73a2302276fcda1/src/odhcp6c.c:1055:29: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
 1055 |                         sep = strpbrk(src, ARRAY_SEP);
      |                             ^
/builddir/build/BUILD/odhcp6c-0-build/odhcp6c-96d9e0b6e81330c61c954c6bc73a2302276fcda1/src/odhcp6c.c: In function ‘parse_opt_dns_string’:
/builddir/build/BUILD/odhcp6c-0-build/odhcp6c-96d9e0b6e81330c61c954c6bc73a2302276fcda1/src/odhcp6c.c:1064:21: error: initialization discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
 1064 |         char *sep = strpbrk(src, ARRAY_SEP);
      |                     ^~~~~~~
/builddir/build/BUILD/odhcp6c-0-build/odhcp6c-96d9e0b6e81330c61c954c6bc73a2302276fcda1/src/odhcp6c.c:1091:29: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
 1091 |                         sep = strpbrk(src, ARRAY_SEP);
      |                             ^
/builddir/build/BUILD/odhcp6c-0-build/odhcp6c-96d9e0b6e81330c61c954c6bc73a2302276fcda1/src/odhcp6c.c: In function ‘parse_opt_ip6’:
/builddir/build/BUILD/odhcp6c-0-build/odhcp6c-96d9e0b6e81330c61c954c6bc73a2302276fcda1/src/odhcp6c.c:1100:21: error: initialization discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
 1100 |         char *sep = strpbrk(src, ARRAY_SEP);
      |                     ^~~~~~~
/builddir/build/BUILD/odhcp6c-0-build/odhcp6c-96d9e0b6e81330c61c954c6bc73a2302276fcda1/src/odhcp6c.c:1124:29: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
 1124 |                         sep = strpbrk(src, ARRAY_SEP);
      |                             ^
/builddir/build/BUILD/odhcp6c-0-build/odhcp6c-96d9e0b6e81330c61c954c6bc73a2302276fcda1/src/odhcp6c.c: In function ‘parse_opt_user_class’:
/builddir/build/BUILD/odhcp6c-0-build/odhcp6c-96d9e0b6e81330c61c954c6bc73a2302276fcda1/src/odhcp6c.c:1133:21: error: initialization discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
 1133 |         char *sep = strpbrk(src, ARRAY_SEP);
      |                     ^~~~~~~
/builddir/build/BUILD/odhcp6c-0-build/odhcp6c-96d9e0b6e81330c61c954c6bc73a2302276fcda1/src/odhcp6c.c:1161:29: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
 1161 |                         sep = strpbrk(src, ARRAY_SEP);
      |                             ^
/builddir/build/BUILD/odhcp6c-0-build/odhcp6c-96d9e0b6e81330c61c954c6bc73a2302276fcda1/src/odhcp6c.c: In function ‘parse_opt’:
/builddir/build/BUILD/odhcp6c-0-build/odhcp6c-96d9e0b6e81330c61c954c6bc73a2302276fcda1/src/odhcp6c.c:1212:14: error: assignment discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
 1212 |         data = strpbrk(opt, ":");
      |              ^
cc1: all warnings being treated as errors
gmake[2]: *** [CMakeFiles/odhcp6c.dir/build.make:82: CMakeFiles/odhcp6c.dir/src/odhcp6c.c.o] Error 1

See:
https://bugzilla.redhat.com/show_bug.cgi?id=2434883
https://fedoraproject.org/wiki/Fedora_44_GCC_16_mass_prebuild#Discarding_const_qualifiers_of_input_arguments_to_string_functions