Build failure with -std=gnu23 (GCC 15 default)

[thesamesam]

When building with GCC trunk which now defaults to -std=gnu23, I get the following:

/bin/sh ../../libtool  --mode=compile x86_64-pc-linux-gnu-gcc -c -I../../include -I../.. -I. -I. -DLIBDIR=\"/usr/lib64\" -DLOCALEDIR=\"/usr/share/locale\" -D_PATH_SUDOERS=\"/etc/sudoers\" -D_PATH_CVTSUDOERS_CONF=\"/etc/cvtsudoers.conf\" -DSUDOERS_UID=0 -DSUDOERS_GID=0 -DSUDOERS_MODE=0440 -DZLIB_CONST -march=native -O3 -pipe  -flto=jobserver -Warray-bounds -fdiagnostics-details -Wstringop-overread -Wstringop-overflow -Wstringop-truncation -fvisibility=hidden  -fPIE  ./policy.c
./policy.c:1361:44: error: initialization of 'int (*)(void)' from incompatible pointer type 'int (*)(const char *, const char *, int,  void *)' [-Wincompatible-pointer-types]
 1361 |     { SUDO_HOOK_VERSION, SUDO_HOOK_SETENV, sudoers_hook_setenv, NULL },
      |                                            ^~~~~~~~~~~~~~~~~~~
./policy.c:1361:44: note: (near initialization for 'sudoers_hooks[0].hook_fn')
./policy.c:1362:46: error: initialization of 'int (*)(void)' from incompatible pointer type 'int (*)(const char *, void *)' [-Wincompatible-pointer-types]
 1362 |     { SUDO_HOOK_VERSION, SUDO_HOOK_UNSETENV, sudoers_hook_unsetenv, NULL },
      |                                              ^~~~~~~~~~~~~~~~~~~~~
./policy.c:1362:46: note: (near initialization for 'sudoers_hooks[1].hook_fn')
./policy.c:1363:44: error: initialization of 'int (*)(void)' from incompatible pointer type 'int (*)(const char *, char **, void *)' [-Wincompatible-pointer-types]
 1363 |     { SUDO_HOOK_VERSION, SUDO_HOOK_GETENV, sudoers_hook_getenv, NULL },
      |                                            ^~~~~~~~~~~~~~~~~~~
./policy.c:1363:44: note: (near initialization for 'sudoers_hooks[2].hook_fn')
./policy.c:1364:44: error: initialization of 'int (*)(void)' from incompatible pointer type 'int (*)(char *, void *)' [-Wincompatible-pointer-types]
 1364 |     { SUDO_HOOK_VERSION, SUDO_HOOK_PUTENV, sudoers_hook_putenv, NULL },
      |                                            ^~~~~~~~~~~~~~~~~~~
./policy.c:1364:44: note: (near initialization for 'sudoers_hooks[3].hook_fn')

C23 removes unprototyped functions and foo() starts to mean foo(void).

[thesamesam]

include/sudo_plugin.h has:

#if defined(__GNUC__) && ((__GNUC__ == 4 && __GNUC_MINOR__ >= 4) || __GNUC__ > 4)
# pragma GCC diagnostic ignored "-Wstrict-prototypes"
#endif

which would've flagged this. It goes back to 4e44bd4.

[millert]

9613ef9 works around this with casts. In the future the hook API may be dropped as it can't really function as intended with modern C libraries.