Cast hook functions to sudo_hook_fn_t to fix C23 compile error.

The sudo plugin API defines sudo_hook_fn_t as a function with
unspecified arguments.  This is no longer supported in C23 so use
a variadic function for sudo_hook_fn_t instead.  Moving to a union
may be a better long-term fix.  GitHub issue #420.

include/sudo_plugin.h

@@ -96,7 +96,11 @@ typedef int (*sudo_printf_t)(int msg_type, const char * restrict fmt, ...);
 #endif
 
 /* Hook functions typedefs. */
+#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 202311L)
+typedef int (*sudo_hook_fn_t)(...);
+#else
 typedef int (*sudo_hook_fn_t)();
+#endif
 typedef int (*sudo_hook_fn_setenv_t)(const char *name, const char *value, int overwrite, void *closure);
 typedef int (*sudo_hook_fn_putenv_t)(char *string, void *closure);
 typedef int (*sudo_hook_fn_getenv_t)(const char *name, char **value, void *closure);

plugins/sudoers/policy.c

@@ -1358,10 +1358,10 @@ sudoers_policy_version(int verbose)
 }
 
 static struct sudo_hook sudoers_hooks[] = {
-    { SUDO_HOOK_VERSION, SUDO_HOOK_SETENV, sudoers_hook_setenv, NULL },
-    { SUDO_HOOK_VERSION, SUDO_HOOK_UNSETENV, sudoers_hook_unsetenv, NULL },
-    { SUDO_HOOK_VERSION, SUDO_HOOK_GETENV, sudoers_hook_getenv, NULL },
-    { SUDO_HOOK_VERSION, SUDO_HOOK_PUTENV, sudoers_hook_putenv, NULL },
+    { SUDO_HOOK_VERSION, SUDO_HOOK_SETENV, (sudo_hook_fn_t)sudoers_hook_setenv, NULL },
+    { SUDO_HOOK_VERSION, SUDO_HOOK_UNSETENV, (sudo_hook_fn_t)sudoers_hook_unsetenv, NULL },
+    { SUDO_HOOK_VERSION, SUDO_HOOK_GETENV, (sudo_hook_fn_t)sudoers_hook_getenv, NULL },
+    { SUDO_HOOK_VERSION, SUDO_HOOK_PUTENV, (sudo_hook_fn_t)sudoers_hook_putenv, NULL },
     { 0, 0, NULL, NULL }
 };
 

src/hooks.c

@@ -125,7 +125,7 @@ process_hooks_unsetenv(const char *name)
 /* Hook registration internals. */
 static int
 register_hook_internal(struct sudo_hook_list *head,
-    int (*hook_fn)(), void *closure)
+    sudo_hook_fn_t hook_fn, void *closure)
 {
     struct sudo_hook_entry *hook;
     debug_decl(register_hook_internal, SUDO_DEBUG_HOOKS);
@@ -185,7 +185,7 @@ register_hook(struct sudo_hook *hook)
 /* Hook deregistration internals. */
 static void
 deregister_hook_internal(struct sudo_hook_list *head,
-    int (*hook_fn)(), void *closure)
+    sudo_hook_fn_t hook_fn, void *closure)
 {
     struct sudo_hook_entry *hook, *prev = NULL;
     debug_decl(deregister_hook_internal, SUDO_DEBUG_HOOKS);