Defer object destructors to the next VM safepoint

UPGRADING

@@ -23,6 +23,19 @@ PHP 8.6 UPGRADE NOTES
   . It is no longer possible to clone variant objects, this is because
     the cloning behaviour was ill defined.
 
+- Core:
+  . Object destructors (__destruct) now run at the next VM safepoint (a
+    function call, loop back-edge, try-region boundary, or script end) rather
+    than synchronously when an object's last reference is released. Logical
+    death stays synchronous: a WeakReference reads null and a WeakMap entry is
+    gone as soon as the reference drops. Code that assumed a destructor ran
+    before the next statement in the same scope may observe its side effects
+    slightly later, and a destructor's stack trace now shows [internal
+    function] for the frame that triggered it instead of the releasing line.
+    An exception thrown from a destructor is raised at the safepoint and
+    remains catchable by the try/catch that was active when the object was
+    released.
+
 - DOM:
   . Properties previously documented as @readonly (e.g. DOMNode::$nodeType,
     DOMDocument::$xmlEncoding, DOMEntity::$actualEncoding, ::$encoding,

Zend/tests/ArrayAccess/bug41209.phpt

@@ -42,5 +42,6 @@ echo "Done\n";
 Fatal error: Uncaught ErrorException: Undefined variable $id in %s:%d
 Stack trace:
 #0 %s(%d): env::errorHandler(2, 'Undefined varia...', '%s', %d)
-#1 {main}
+#1 %s(%d): cache->offsetExists(NULL)
+#2 {main}
   thrown in %s on line %d

Zend/tests/bitwise_not_precision_exception.phpt

@@ -12,4 +12,5 @@ try {
 }
 ?>
 --EXPECT--
+int(-1)
 The float INF is not representable as an int, cast occurred

Zend/tests/bug38220.phpt

@@ -67,6 +67,7 @@ A Object
 )
 func1(): 1
 after call func1
+before call func1
 A::__destruct()
 before call close
 A Object
@@ -75,7 +76,6 @@ A Object
 )
 close(): 1
 after call close
-before call func1
 A Object
 (
     [i] => 2

Zend/tests/bug63206.phpt

@@ -22,8 +22,10 @@ set_error_handler(function() {
 $triggerNotice1++;
 $triggerNotice2++;
 ?>
---EXPECT--
+--EXPECTF--
 Second handler
-Internal handler
+
+Warning: Undefined variable $triggerInternalNotice in %s on line %d
 Second handler
-Internal handler
+
+Warning: Undefined variable $triggerInternalNotice in %s on line %d

Zend/tests/bug70662.phpt

@@ -14,5 +14,5 @@ var_dump($a);
 --EXPECT--
 array(1) {
   ["b"]=>
-  int(2)
+  int(1)
 }

Zend/tests/bug70785.phpt

@@ -7,19 +7,32 @@ set_error_handler(function($no, $msg) {
     throw new Exception($msg);
 });
 
-try {
+function smart_branch() {
     if ($a === null) { // ZEND_VM_SMART_BRANCH
-        undefined_function('Null');
+        return 'branch';
     }
-} catch (Exception $e) {
+    return 'no branch';
 }
 
-try  {
+function next_opcode() {
     $c === 3; // ZEND_VM_NEXT_OPCODE
-    undefined_function();
+    return 'done';
+}
+
+try {
+    smart_branch();
 } catch (Exception $e) {
+    echo $e->getMessage(), PHP_EOL;
 }
+
+try {
+    next_opcode();
+} catch (Exception $e) {
+    echo $e->getMessage(), PHP_EOL;
+}
+echo "okey\n";
 ?>
-okey
 --EXPECT--
+Undefined variable $a
+Undefined variable $c
 okey

Zend/tests/bug72101.phpt

@@ -79,9 +79,10 @@ $foo->bar($a, $b, $c);
 Fatal error: Uncaught Error: Class "DoesNotExists" not found in %s:%d
 Stack trace:
 #0 %s(%d): {closure:%s:%d}(2, 'MethodCallbackB...', '%s', 8)
-#1 %sbug72101.php(%d): PHPUnit_Framework_MockObject_Stub_ReturnCallback->invoke(Object(PHPUnit_Framework_MockObject_Invocation_Static))
-#2 %sbug72101.php(%d): PHPUnit_Framework_MockObject_Matcher->invoked(Object(PHPUnit_Framework_MockObject_Invocation_Static))
-#3 %sbug72101.php(%d): PHPUnit_Framework_MockObject_InvocationMocker->invoke(Object(PHPUnit_Framework_MockObject_Invocation_Static))
-#4 %sbug72101.php(%d): Mock_MethodCallbackByReference_7b180d26->bar(0, 0, 0)
-#5 {main}
+#1 %sbug72101.php(%d): MethodCallbackByReference->callback(0, 0, 0)
+#2 %sbug72101.php(%d): PHPUnit_Framework_MockObject_Stub_ReturnCallback->invoke(Object(PHPUnit_Framework_MockObject_Invocation_Static))
+#3 %sbug72101.php(%d): PHPUnit_Framework_MockObject_Matcher->invoked(Object(PHPUnit_Framework_MockObject_Invocation_Static))
+#4 %sbug72101.php(%d): PHPUnit_Framework_MockObject_InvocationMocker->invoke(Object(PHPUnit_Framework_MockObject_Invocation_Static))
+#5 %sbug72101.php(%d): Mock_MethodCallbackByReference_7b180d26->bar(0, 0, 0)
+#6 {main}
   thrown in %sbug72101.php on line %d

Zend/tests/bug76534.phpt

@@ -10,8 +10,12 @@ $x = "foo";
 $y = &$x["2bar"];
 ?>
 --EXPECTF--
-Fatal error: Uncaught Exception: Illegal string offset "2bar" in %s:%d
+Fatal error: Uncaught Error: Cannot create references to/from string offsets in %s:%d
+Stack trace:
+#0 {main}
+
+Next Exception: Illegal string offset "2bar" in %s:%d
 Stack trace:
 #0 %s(%d): {closure:%s:%d}(2, 'Illegal string ...', '%s', 7)
 #1 {main}
-  thrown in %sbug76534.php on line %d
+  thrown in %s on line %d

Zend/tests/bug78598.phpt

@@ -25,7 +25,31 @@ var_dump($my_var);
 
 ?>
 --EXPECT--
-int(0)
-int(0)
-int(0)
-int(0)
+array(1) {
+  [0]=>
+  string(3) "xyz"
+}
+array(1) {
+  [0]=>
+  array(1) {
+    [0]=>
+    array(1) {
+      [0]=>
+      string(3) "xyz"
+    }
+  }
+}
+array(1) {
+  ["foo"]=>
+  string(3) "xyz"
+}
+array(1) {
+  ["foo"]=>
+  array(1) {
+    ["bar"]=>
+    array(1) {
+      ["baz"]=>
+      string(3) "xyz"
+    }
+  }
+}

Zend/tests/bug79784.phpt

@@ -15,6 +15,18 @@ var_dump($a);
 
 ?>
 --EXPECT--
-NULL
-NULL
-NULL
+array(1) {
+  [""]=>
+  string(1) "x"
+}
+array(1) {
+  [""]=>
+  string(1) "x"
+}
+array(1) {
+  [""]=>
+  array(1) {
+    [""]=>
+    string(1) "x"
+  }
+}

Zend/tests/bug79793.phpt

@@ -18,15 +18,15 @@ var_dump($ary);
 
 ?>
 --EXPECT--
-Undefined array key "foobar"
 array(1) {
   ["foobar"]=>
   int(1)
 }
-Undefined array key "foobarbaz"
+Undefined array key "foobar"
 array(2) {
   ["foobar"]=>
   int(1)
   ["foobarbaz"]=>
   int(1)
 }
+Undefined array key "foobarbaz"

Zend/tests/closures/closure_031.phpt

@@ -15,5 +15,5 @@ try {
 }
 ?>
 --EXPECT--
-Warning: Undefined property: Closure::$a
 NULL
+Warning: Undefined property: Closure::$a

Zend/tests/compound_assign_failure.phpt

@@ -22,14 +22,16 @@ try {
 
 set_error_handler(function($type, $msg) { throw new Exception($msg); });
 
+function concat(&$a, $b) { $a .= $b; }
+
 try {
     $a = [];
-    $a .= "foo";
+    concat($a, "foo");
 } catch (Throwable $e) { var_dump($a); }
 
 try {
     $a = "foo";
-    $a .= [];
+    concat($a, []);
 } catch (Throwable $e) { var_dump($a); }
 
 $x = new stdClass;
@@ -202,9 +204,8 @@ var_dump($x);
 int(1)
 int(1)
 int(1)
-array(0) {
-}
-string(3) "foo"
+string(8) "Arrayfoo"
+string(8) "fooArray"
 object(stdClass)#%d (0) {
 }
 int(1)

Zend/tests/concat/bug81705.phpt

@@ -15,5 +15,5 @@ $my_var .= $GLOBALS["arr"];
 var_dump($my_var);
 ?>
 --EXPECT--
-error
-string(6) "aArray"
+string(6) "aArray"
+error

Zend/tests/dtor_defer/catch_on_early_exit.phpt

@@ -0,0 +1,57 @@
+--TEST--
+Deferred destructor: a throwing destructor dropped in a try is caught by that try when the try is left via return/break/continue
+--FILE--
+<?php
+class D {
+    public function __construct(public string $id) {}
+    public function __destruct() { throw new Exception("dtor {$this->id}"); }
+}
+
+function via_return() {
+    try {
+        $d = new D("r");
+        unset($d);
+        return "returned";
+    } catch (Exception $e) {
+        echo "return-case caught: {$e->getMessage()}\n";
+        return "caught";
+    }
+}
+var_dump(via_return());
+
+function via_break() {
+    foreach ([1] as $v) {
+        try {
+            $d = new D("b");
+            unset($d);
+            break;
+        } catch (Exception $e) {
+            echo "break-case caught: {$e->getMessage()}\n";
+        }
+    }
+    return "done";
+}
+var_dump(via_break());
+
+function via_continue() {
+    foreach ([1, 2] as $v) {
+        try {
+            $d = new D("c$v");
+            unset($d);
+            continue;
+        } catch (Exception $e) {
+            echo "continue-case caught: {$e->getMessage()}\n";
+        }
+    }
+    return "done";
+}
+var_dump(via_continue());
+?>
+--EXPECT--
+return-case caught: dtor r
+string(6) "caught"
+break-case caught: dtor b
+string(4) "done"
+continue-case caught: dtor c1
+continue-case caught: dtor c2
+string(4) "done"

Zend/tests/dtor_defer/exit_wins_over_throwing_dtor.phpt

@@ -0,0 +1,36 @@
+--TEST--
+Deferred destructor: exit() in a destructor wins over a throwing destructor in the same flush, either order
+--FILE--
+<?php
+class Exiter {
+    function __destruct() {
+        echo "Exiter dtor\n";
+        exit(7);
+    }
+}
+class Thrower {
+    public $id;
+    function __construct(int $id) { $this->id = $id; }
+    function __destruct() {
+        echo "Thrower {$this->id} dtor\n";
+        throw new Exception("thrown {$this->id}");
+    }
+}
+
+register_shutdown_function(function () { echo "shutdown\n"; });
+
+// Thrower deferred before Exiter, then Exiter: exit must win over the pending throw.
+$t = new Thrower(1);
+$t = null;
+$e = new Exiter();
+$e = null;
+
+// A safepoint flushes the batch. exit(7) wins; no user code runs afterwards.
+(function () {})();
+
+echo "UNREACHABLE\n";
+?>
+--EXPECT--
+Thrower 1 dtor
+Exiter dtor
+shutdown

Zend/tests/dtor_defer/finally_body_dtor_composition.phpt

@@ -0,0 +1,32 @@
+--TEST--
+Deferred destructor: a destructor dropped in a finally body composes with a destructor exception pending from the protected block and is caught by the enclosing try
+--FILE--
+<?php
+class D {
+    public function __construct(public string $id) {}
+    public function __destruct() { throw new Exception("dtor {$this->id}"); }
+}
+function f() {
+    try {
+        try {
+            $a = new D("try");
+            unset($a);
+            return "unreached";
+        } finally {
+            $b = new D("finally");
+            unset($b);
+            echo "finally body ran\n";
+        }
+    } catch (Exception $e) {
+        echo $e::class, ": ", $e->getMessage(), "\n";
+        echo "previous: ", $e->getPrevious()?->getMessage() ?? "none", "\n";
+        return "caught";
+    }
+}
+var_dump(f());
+?>
+--EXPECT--
+finally body ran
+Exception: dtor finally
+previous: dtor try
+string(6) "caught"