Fix GH-21699: don't treat callables as valid if exception pending after deprecations

When resolving string callables using self::, parent::, or static::,
zend_is_callable_check_class() emits E_DEPRECATED. If the user error
handler throws, EG(exception) is set but the function could still
return true, leading to trampoline allocation and a failed assertion
in shutdown_executor().

Return false from zend_is_callable_check_class() when EG(exception)
is set after handling.

Add regression tests for self::, parent::, and static:: forms.

Author: macoaure

NEWS

@@ -3,6 +3,8 @@ PHP                                                                        NEWS
 ?? ??? ????, PHP 8.6.0alpha1
 
 - Core:
+  . Fixed bug GH-21699 (Assertion failure in shutdown_executor when resolving
+    self::/parent::/static:: callables if the error handler throws).
   . Added first-class callable cache to share instances for the duration of the
     request. (ilutov)
   . It is now possible to use reference assign on WeakMap without the key

Zend/tests/gh_21699.phpt

@@ -0,0 +1,31 @@
+--TEST--
+GH-21699: Assertion failure in shutdown_executor when error handler throws during self:: callable resolution
+--FILE--
+<?php
+set_error_handler(function () {
+    throw new Exception;
+});
+class bar {
+    public static function __callstatic($fusion, $b)
+    {
+    }
+    public function test()
+    {
+        call_user_func('self::y');
+    }
+}
+$x = new bar;
+$x->test();
+?>
+--EXPECTF--
+Fatal error: Uncaught Exception in %s:%d
+Stack trace:
+#0 %s(%d): {closure:%s}(%d, 'Use of "self" i%s', '%s', %d)
+#1 %s(%d): bar->test()
+#2 {main}
+
+Next TypeError: call_user_func(): Argument #1 ($callback) must be a valid callback, (null) in %s:%d
+Stack trace:
+#0 %s(%d): bar->test()
+#1 {main}
+  thrown in %s on line %d

Zend/tests/gh_21699_parent.phpt

@@ -0,0 +1,32 @@
+--TEST--
+GH-21699 (parent::): no shutdown_executor trampoline assertion when error handler throws during parent:: callable resolution
+--FILE--
+<?php
+set_error_handler(function () {
+    throw new Exception;
+});
+class Base {
+    public static function __callStatic($name, $args)
+    {
+    }
+}
+class Child extends Base {
+    public function test()
+    {
+        call_user_func('parent::missing');
+    }
+}
+(new Child)->test();
+?>
+--EXPECTF--
+Fatal error: Uncaught Exception in %s:%d
+Stack trace:
+#0 %s(%d): {closure:%s}(%d, 'Use of "parent"%s', '%s', %d)
+#1 %s(%d): Child->test()
+#2 {main}
+
+Next TypeError: call_user_func(): Argument #1 ($callback) must be a valid callback, (null) in %s:%d
+Stack trace:
+#0 %s(%d): Child->test()
+#1 {main}
+  thrown in %s on line %d

Zend/tests/gh_21699_static.phpt

@@ -0,0 +1,31 @@
+--TEST--
+GH-21699 (static::): no shutdown_executor trampoline assertion when error handler throws during static:: callable resolution
+--FILE--
+<?php
+set_error_handler(function () {
+    throw new Exception;
+});
+class bar {
+    public static function __callstatic($fusion, $b)
+    {
+    }
+    public function test()
+    {
+        call_user_func('static::y');
+    }
+}
+$x = new bar;
+$x->test();
+?>
+--EXPECTF--
+Fatal error: Uncaught Exception in %s:%d
+Stack trace:
+#0 %s(%d): {closure:%s}(%d, 'Use of "static"%s', '%s', %d)
+#1 %s(%d): bar->test()
+#2 {main}
+
+Next TypeError: call_user_func(): Argument #1 ($callback) must be a valid callback, (null) in %s:%d
+Stack trace:
+#0 %s(%d): bar->test()
+#1 {main}
+  thrown in %s on line %d

Zend/zend_API.c

@@ -3770,6 +3770,10 @@ static bool zend_is_callable_check_class(zend_string *name, zend_class_entry *sc
 		if (error) zend_spprintf(error, 0, "class \"%.*s\" not found", (int)name_len, ZSTR_VAL(name));
 	}
 	ZSTR_ALLOCA_FREE(lcname, use_heap);
+	/* User error handlers may throw from deprecations above; do not report callable as valid. */
+	if (UNEXPECTED(EG(exception))) {
+		return false;
+	}
 	return ret;
 }
 /* }}} */