Fix GH-16414: Segmentation fault in Zend/zend_observer.c

Author: cmb69

Zend/zend_observer.c

@@ -169,6 +169,9 @@ static bool zend_observer_remove_handler(void **first_handler, void *old_handler
 
 ZEND_API void zend_observer_add_begin_handler(zend_function *function, zend_observer_fcall_begin_handler begin) {
 	size_t registered_observers = zend_observers_fcall_list.count;
+	if (registered_observers == 0) {
+		return;
+	}
 	zend_observer_fcall_begin_handler *first_handler = (void *)&ZEND_OBSERVER_DATA(function), *last_handler = first_handler + registered_observers - 1;
 	if (*first_handler == ZEND_OBSERVER_NOT_OBSERVED) {
 		*first_handler = begin;
@@ -190,6 +193,9 @@ ZEND_API bool zend_observer_remove_begin_handler(zend_function *function, zend_o
 
 ZEND_API void zend_observer_add_end_handler(zend_function *function, zend_observer_fcall_end_handler end) {
 	size_t registered_observers = zend_observers_fcall_list.count;
+	if (registered_observers == 0) {
+		return;
+	}
 	zend_observer_fcall_end_handler *end_handler = (zend_observer_fcall_end_handler *)&ZEND_OBSERVER_DATA(function) + registered_observers;
 	// to allow to preserve the invariant that end handlers are in reverse order of begin handlers, push the new end handler in front
 	if (*end_handler != ZEND_OBSERVER_NOT_OBSERVED) {

ext/zend_test/tests/gh16414.phpt

@@ -0,0 +1,10 @@
+--TEST--
+GH-16414 (Segmentation fault in Zend/zend_observer.c)
+--EXTENSIONS--
+zend_test
+--FILE--
+<?php
+function bar() {}
+ini_set("zend_test.observer.observe_function_names", "bar");
+?>
+--EXPECT--