Add trampoline test for generic XMLParser handler

Author: Girgias

ext/xml/tests/set_handler_trampoline.phpt

@@ -0,0 +1,33 @@
+--TEST--
+Test XMLParser generic handlers as trampoline callback
+--EXTENSIONS--
+xml
+--FILE--
+<?php
+class TrampolineTest {
+    public function __call(string $name, array $arguments) {
+        echo 'Trampoline for ', $name, PHP_EOL;
+        echo 'Target: ', $arguments[1], PHP_EOL;
+        echo 'Data: ', $arguments[2], PHP_EOL;
+    }
+}
+
+$o = new TrampolineTest();
+$callback = [$o, 'pi_handler'];
+
+$xml = <<<HERE
+<?xml version="1.0" encoding="ISO-8859-1"?>
+<?xml-stylesheet href="default.xsl" type="text/xml"?>
+HERE;
+
+/* Use xml_set_processing_instruction_handler() for generic implementation */
+$parser = xml_parser_create();
+xml_set_processing_instruction_handler($parser, $callback);
+xml_parse($parser, $xml, true);
+xml_parser_free($parser);
+
+?>
+--EXPECT--
+Trampoline for pi_handler
+Target: xml-stylesheet
+Data: href="default.xsl" type="text/xml"

ext/xml/xml.c

@@ -1203,7 +1203,7 @@ static void php_xml_set_handler_parse_callable(
 			/* Free handler, so just return and a uninitialized FCC communicates this */
 			return;
 		}
-		if (!ZEND_FCC_INITIALIZED(handler_fcc)) { // TODO: cover this with a test, this is never executed right now
+		if (!ZEND_FCC_INITIALIZED(handler_fcc)) {
 			zend_is_callable_ex(&handler_fci.function_name, NULL, IS_CALLABLE_SUPPRESS_DEPRECATIONS, NULL, &handler_fcc, NULL);
 			/* Call trampoline has been cleared by zpp. Refetch it, because we want to deal
 			 * with it ourselves. It is important that it is not refetched on every call,