https://bugs.gentoo.org/874759
--- a/configure
+++ b/configure
@@ -65,9 +65,9 @@ ac_prog_ranlib_v
 
 ac_ign ac_yesno "for getopt()" ac_have GETOPT ac_link <<EOF
 #include <stdio.h>
+#include <unistd.h>
 extern int optind;
 extern char *optarg;
-extern int getopt(int, char **, char *);
 int main(int argc, char **argv) {
   getopt(argc, argv, "abc");
   return optarg ? optind : 0;
@@ -75,7 +75,8 @@ int main(int argc, char **argv) {
 EOF
 
 if ac_library_find_v 'socket and connect' "" "-lsocket -lnsl" <<EOF
-int main() { socket(); connect(); return 0; }
+#include <sys/socket.h>
+int main() { socket(0, 0, 0); connect(0, 0, 0); return 0; }
 EOF
 then :
 else