https://github.com/arineng/rwhoisd/pull/3/commits/285e84dddee471886d84da3ea3579facb9fe7e99

From 285e84dddee471886d84da3ea3579facb9fe7e99 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20P=C3=ADsa=C5=99?= <ppisar@redhat.com>
Date: Fri, 1 Dec 2023 13:32:08 +0100
Subject: [PATCH] Fix a return value of signal handlers
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GCC 14 will error if a value returned from a function does not match
a function prototype. This can be reproduced with -Wreturn-mismatch
option and is a problem compilers where a signal handler should return
void:

    daemon.c: In function ‘sigchld_handler’:
    daemon.c:108:10: error: ‘return’ with a value, in function returning void
      108 |   return 0;
      |          ^
    daemon.c:92:1: note: declared here
       92 | sigchld_handler(
      | ^~~~~~~~~~~~~~~
    daemon.c: In function ‘sighup_handler’:
    daemon.c:117:10: error: ‘return’ with a value, in function returning void
      117 |   return 0;
      |          ^
    daemon.c:112:1: note: declared here
      112 | sighup_handler(
      | ^~~~~~~~~~~~~~
    daemon.c: In function ‘exit_handler’:
    daemon.c:127:10: error: ‘return’ with a value, in function returning void
      127 |   return 0;
      |          ^

This patch fixes it.
---
 rwhoisd/configure.ac    | 3 +++
 rwhoisd/server/daemon.c | 6 ++++++
 2 files changed, 9 insertions(+)

diff --git a/configure.ac b/configure.ac
index 0b822ac..b1d659f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -114,6 +114,9 @@ AC_CHECK_FUNCS(getcwd gethostname socket strftime uname flock lockf \
 	       setsid crypt memset memcpy usleep wait3 getaddrinfo vsnprintf)
 AC_REPLACE_FUNCS(strerror)
 
+AS_IF([test "${ac_cv_type_signal}" = "int"],
+    AC_DEFINE([RETSIGTYPE_IS_INT], [1], [Define if RETSIGTYPE is int.])
+    )
 
 dnl Optional software.
 
diff --git a/server/daemon.c b/server/daemon.c
index a5c638b..c943da9 100644
--- a/server/daemon.c
+++ b/server/daemon.c
@@ -105,7 +105,9 @@ sigchld_handler(
   /* reset the signal handler -- some older systems remove the signal
      handler upon use.  POSIX systems should not do this */
   signal(SIGCHLD, (__sighandler_t)sigchld_handler);
+#ifdef RETSIGTYPE_IS_INT
   return 0;
+#endif
 }
 
 static RETSIGTYPE
@@ -114,7 +116,9 @@ sighup_handler(
 {
   hup_recvd = TRUE;
   signal(SIGHUP, (__sighandler_t)sighup_handler);
+#ifdef RETSIGTYPE_IS_INT
   return 0;
+#endif
 }
 
 static RETSIGTYPE
@@ -124,7 +128,9 @@ exit_handler(
   log(L_LOG_NOTICE, UNKNOWN, "Exiting");
   delpid();
   exit(0);
+#ifdef RETSIGTYPE_IS_INT
   return 0;
+#endif
 }
 
 static void set_sighup (void)