https://bugs.gentoo.org/898234
--- a/configure.in
+++ b/configure.in
@@ -62,7 +62,7 @@ if test "x$GDK_IMLIB" != x; then
 #include <glib.h>
 #include <gmodule.h>
 #include <stdlib.h>
-main ()
+int main ()
 {
     if (g_module_supported ())
         exit (0);
@@ -166,6 +166,7 @@ if test "x$enable_shm" = "xyes"; then
           #include <sys/types.h>
           #include <sys/ipc.h>
           #include <sys/shm.h>
+          #include <stdlib.h>
           int main()
           {
             int id;