--- ./configure.orig
+++ ./configure
@@ -17436,11 +17436,11 @@
 #ifdef __cplusplus
 extern "C"
 #endif
-char isinf ();
+#include <math.h>
 int
 main ()
 {
-return isinf ();
+return isinf (0.0);
   ;
   return 0;
 }