Fix GH-16414: zend_test.observer.observe_function_names may segfault

Unless `zend_test.observer.enabled` is on, we must not add observer
handlers, so we let the INI modify handler fail early.

We also need to ensure that the functions to observe have already been
called, so that their begin and end handlers are properly initialized.
Otherwise we will not observe the function execution, but a segfault.

Co-authored-by: Bob Weinand <[email protected]>

Closes GH-16438.

Author: cmb69

ext/zend_test/observer.c

@@ -304,9 +304,12 @@ static ZEND_INI_MH(zend_test_observer_OnUpdateCommaList)
 	zend_array **p = (zend_array **) ZEND_INI_GET_ADDR();
 	zend_string *funcname;
 	zend_function *func;
+	if (!ZT_G(observer_enabled)) {
+		return FAILURE;
+	}
 	if (stage != PHP_INI_STAGE_STARTUP && stage != PHP_INI_STAGE_ACTIVATE && stage != PHP_INI_STAGE_DEACTIVATE && stage != PHP_INI_STAGE_SHUTDOWN) {
 		ZEND_HASH_FOREACH_STR_KEY(*p, funcname) {
-			if ((func = zend_hash_find_ptr(EG(function_table), funcname))) {
+			if ((func = zend_hash_find_ptr(EG(function_table), funcname)) && ZEND_OBSERVER_DATA(func) != NULL) {
 				void *old_handler;
 				zend_observer_remove_begin_handler(func, observer_begin, (zend_observer_fcall_begin_handler *)&old_handler);
 				zend_observer_remove_end_handler(func, observer_end, (zend_observer_fcall_end_handler *)&old_handler);
@@ -329,7 +332,7 @@ static ZEND_INI_MH(zend_test_observer_OnUpdateCommaList)
 		zend_string_release(str);
 		if (stage != PHP_INI_STAGE_STARTUP && stage != PHP_INI_STAGE_ACTIVATE && stage != PHP_INI_STAGE_DEACTIVATE && stage != PHP_INI_STAGE_SHUTDOWN) {
 			ZEND_HASH_FOREACH_STR_KEY(*p, funcname) {
-				if ((func = zend_hash_find_ptr(EG(function_table), funcname))) {
+				if ((func = zend_hash_find_ptr(EG(function_table), funcname)) && ZEND_OBSERVER_DATA(func) != NULL) {
 					zend_observer_add_begin_handler(func, observer_begin);
 					zend_observer_add_end_handler(func, observer_end);
 				}

ext/zend_test/tests/gh16414.phpt

@@ -0,0 +1,13 @@
+--TEST--
+GH-16414 (zend_test.observer.observe_function_names may segfault)
+--EXTENSIONS--
+zend_test
+--INI--
+zend_test.observer.enabled=0
+--FILE--
+<?php
+function bar() {}
+var_dump(ini_set("zend_test.observer.observe_function_names", "bar"));
+?>
+--EXPECT--
+bool(false)