https://sourceforge.net/p/cups-bjnp/patches/5/
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -25,9 +25,9 @@
 	#include <sys/socket.h> ], [
 	 /* AF_INET6 available check */  
  	if (socket(AF_INET6, SOCK_STREAM, 0) < 0) 
-   	  exit(1); 
+   	  return 1; 
  	else 
-   	  exit(0); 
+   	  return 0; 
       ],[
         AC_MSG_RESULT(yes) 
         AC_DEFINE([ENABLE_IPV6], 1, [Define to 1 if the system supports IPv6]) 
@@ -47,7 +47,7 @@
 	/* test if the ss_family member exists in struct sockaddr_storage */
 	struct sockaddr_storage ss;
 	ss.ss_family = AF_INET;
-	exit (0);
+	return 0;
     ], [
 	AC_MSG_RESULT(yes)
 	AC_DEFINE([HAS_SS_FAMILY], 1, [Define to 1 if struct sockaddr_storage has an ss_family member])
@@ -59,7 +59,7 @@
 		/* test if the __ss_family member exists in struct sockaddr_storage */
 		struct sockaddr_storage ss;
 		ss.__ss_family = AF_INET;
-		exit (0);
+		return 0;
 	  ], [
 		AC_MSG_RESULT([no, but __ss_family exists])
 		AC_DEFINE([HAS___SS_FAMILY], 1, [Define to 1 if struct sockaddr_storage has __ss_family instead of ss_family])