https://github.com/tomac/yersinia/pull/76

From ec9d31932fca39e3160b0d0bfd0383db82ff5bcf Mon Sep 17 00:00:00 2001
From: Sam James <sam@gentoo.org>
Date: Wed, 16 Nov 2022 23:10:45 +0000
Subject: [PATCH] configure: fix -Wimplicit-function-declaration,
 -Wstrict-prototypes

Clang 16 makes -Wimplicit-function-declaration an error by default. Unfortunately,
this can lead to misconfiguration or miscompilation of software as configure
tests may then return the wrong result.

For more information, see LWN.net [0] or LLVM's Discourse [1], the Gentoo wiki [2],
or the (new) c-std-porting mailing list [3].

[0] https://lwn.net/Articles/913505/
[1] https://discourse.llvm.org/t/configure-script-breakage-with-the-new-werror-implicit-function-declaration/65213
[2] https://wiki.gentoo.org/wiki/Modern_C_porting
[3] hosted at lists.linux.dev.

Signed-off-by: Sam James <sam@gentoo.org>
--- a/configure.in
+++ b/configure.in
@@ -233,12 +233,13 @@ dnl fi
 
 AC_MSG_CHECKING(if libnet is at least version 1.1.2)
 AC_TRY_RUN([
-#include<stdio.h>
-#include<libnet.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <libnet.h>
 #define HOPE_MAJOR  1
 #define HOPE_MEDIUM 1
 #define HOPE_MINOR  2
-int main()
+int main(void)
 {
   unsigned int major,medium,minor,current, desired;
   desired = HOPE_MAJOR*10000 + HOPE_MEDIUM*100 + HOPE_MINOR;
@@ -419,9 +420,9 @@ AC_CHECK_FUNCS(strerror_r, have_strerror_r=yes,have_strerror_r=no)
 if test $have_strerror_r = yes; then
 AC_MSG_CHECKING(if strerror_r is on glibc version >= 2.0)
 AC_TRY_RUN([
-#include <stdio.h>
+#include <stdlib.h>
 #include <features.h>
-int main()
+int main(void)
 {
 #if defined(__GLIBC__) && __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 0
    exit(0);