Fixed bug #75097 (gethostname fails if your host name is 64 chars long)

PHP contained two different off-by-one errors, which are fixed here. First,
it created a buffer of size HOST_NAME_MAX, not adding space for a null
terminator. Second, it subtracted 1 from the size of that buffer when passing
its size to gethostname(), despite gethostname() expecting it to be a buffer
size including space for a terminating null byte, not a string length.

NEWS

@@ -8,6 +8,8 @@ PHP                                                                        NEWS
 - CURL:
   . Fixed bug #75093 (OpenSSL support not detected). (Remi)
 
+- Standard:
+  . Fixed bug #75097 (gethostname fails if your host name is 64 chars long). (Andrea)
 
 31 Aug 2017 PHP 7.0.23
 

ext/standard/dns.c

@@ -131,13 +131,13 @@ static zend_string *php_gethostbyname(char *name);
    Get the host name of the current machine */
 PHP_FUNCTION(gethostname)
 {
-	char buf[HOST_NAME_MAX];
+	char buf[HOST_NAME_MAX + 1];
 
 	if (zend_parse_parameters_none() == FAILURE) {
 		return;
 	}
 
-	if (gethostname(buf, sizeof(buf) - 1)) {
+	if (gethostname(buf, sizeof(buf))) {
 		php_error_docref(NULL, E_WARNING, "unable to fetch host [%d]: %s", errno, strerror(errno));
 		RETURN_FALSE;
 	}