Treat invalid characters in basename() consistently

Always simply ignore (pass through) them. Previously the behavior
depended on where the invalid character occurred, as it messed
up the state management.

Author: nikic

ext/standard/string.c

@@ -1515,11 +1515,6 @@ PHPAPI zend_string *php_basename(const char *s, size_t len, char *suffix, size_t
 		int inc_len = (*s == '\0' ? 1 : php_mblen(s, len));
 
 		switch (inc_len) {
-			case -2:
-			case -1:
-				inc_len = 1;
-				php_mb_reset();
-				break;
 			case 0:
 				goto quit_loop;
 			case 1:
@@ -1553,6 +1548,11 @@ PHPAPI zend_string *php_basename(const char *s, size_t len, char *suffix, size_t
 				}
 				break;
 			default:
+				if (inc_len < 0) {
+					/* If character is invalid, treat it like other non-significant characters. */
+					inc_len = 1;
+					php_mb_reset();
+				}
 				if (state == 0) {
 					basename_start = s;
 					state = 1;

ext/standard/tests/strings/basename_invalid_path.phpt

@@ -13,9 +13,12 @@ if((substr(PHP_OS, 0, 3) == "WIN"))
                 If the filename ends in suffix this will also be cut off.
 */
 
-var_dump(basename(chr(-1)));
+setlocale(LC_CTYPE, "C");
+var_dump(bin2hex(basename("\xff")));
+var_dump(bin2hex(basename("a\xffb")));
 
 echo "Done\n";
 --EXPECT--
-string(0) ""
+string(2) "ff"
+string(6) "61ff62"
 Done