Add an assertion about the reallocation

Author: Girgias

sapi/cli/php_cli_server.c

@@ -1670,9 +1670,11 @@ static int php_cli_server_client_read_request_on_header_value(php_http_parser *p
 			client->current_header_value = zend_string_init(at, length, /* persistent */ true);
 			break;
 		case HEADER_VALUE: {
+			/* Assert that there is only one reference to the header value, as then zend_string_extends()
+			 * will reallocate it such that we do not need to release the old value. */
+			ZEND_ASSERT(GC_REFCOUNT(client->current_header_value) == 1);
 			/* Previous element was part of header value, append content to it */
 			size_t old_length = ZSTR_LEN(client->current_header_value);
-			// TODO Release old value?
 			client->current_header_value = zend_string_extend(client->current_header_value, old_length + length, /* persistent */ true);
 			memcpy(ZSTR_VAL(client->current_header_value) + old_length, at, length);
 			// Null terminate