--- configure.orig	2021-03-16 00:55:15.000000000 +1100
+++ configure	2021-03-16 01:09:57.000000000 +1100
@@ -10716,13 +10716,13 @@
       void *foo(void *parm) {
         return NULL;
       }
-      main() {
+      int main() {
         pthread_attr_t attr;
         pthread_t id;
-        if (pthread_attr_init(&attr)) exit(-1);
-        if (pthread_attr_setscope(&attr, PTHREAD_SCOPE_SYSTEM)) exit(-1);
-        if (pthread_create(&id, &attr, foo, NULL)) exit(-1);
-        exit(0);
+        if (pthread_attr_init(&attr)) return (-1);
+        if (pthread_attr_setscope(&attr, PTHREAD_SCOPE_SYSTEM)) return (-1);
+        if (pthread_create(&id, &attr, foo, NULL)) return (-1);
+        return (0);
       }
 _ACEOF
 if ac_fn_c_try_run "$LINENO"; then :
@@ -14473,7 +14473,7 @@
   int main()
   {
 	/* Success: exit code 0 */
-        exit((((wchar_t) -1) < ((wchar_t) 0)) ? 0 : 1);
+        return ((((wchar_t) -1) < ((wchar_t) 0)) ? 0 : 1);
   }
 
 _ACEOF
@@ -14791,7 +14791,7 @@
 
 int main()
 {
-	exit(((-1)>>3 == -1) ? 0 : 1);
+	return (((-1)>>3 == -1) ? 0 : 1);
 }
 
 _ACEOF
@@ -15262,12 +15262,16 @@
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
+#if HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+
 int main()
 {
 	int val1 = nice(1);
 	if (val1 != -1 && val1 == nice(2))
-		exit(0);
-	exit(1);
+		return (0);
+	return (1);
 }
 
 _ACEOF
@@ -15303,6 +15307,9 @@
 /* end confdefs.h.  */
 
 #include <poll.h>
+#if HAVE_UNISTD_H
+#include <unistd.h>
+#endif
 
 int main()
 {