Add API to prevent Fiber switch in select contexts

Co-authored-by: Martin Schröder <m.schroeder2007@gmail.com>

Zend/tests/fibers/invocable-class.phpt

@@ -20,8 +20,8 @@ $fiber = new Fiber($test);
 $fiber->start();
 
 ?>
---EXPECT--
-object(Test)#1 (0) {
+--EXPECTF--
+object(Test)#%d (0) {
 }
-object(Test)#1 (0) {
+object(Test)#%d (0) {
 }

Zend/tests/fibers/no-switch-dtor-resume.phpt

@@ -0,0 +1,30 @@
+--TEST--
+Cannot resume fiber within destructor
+--FILE--
+<?php
+
+$fiber = new Fiber(function () {
+    Fiber::suspend();
+});
+$fiber->start();
+
+return new class ($fiber) {
+    private $fiber;
+
+    public function __construct(Fiber $fiber) {
+        $this->fiber = $fiber;
+    }
+
+    public function __destruct() {
+        $this->fiber->resume(1);
+    }
+};
+
+?>
+--EXPECTF--
+Fatal error: Uncaught FiberError: Cannot switch fibers in current execution context in %sno-switch-dtor-resume.php:%d
+Stack trace:
+#0 %sno-switch-dtor-resume.php(%d): Fiber->resume(1)
+#1 %sno-switch-dtor-resume.php(%d): class@anonymous->__destruct()
+#2 {main}
+  thrown in %sno-switch-dtor-resume.php on line %d

Zend/tests/fibers/no-switch-dtor-start.phpt

@@ -0,0 +1,20 @@
+--TEST--
+Cannot start fiber within destructor
+--FILE--
+<?php
+
+return new class () {
+    public function __destruct() {
+        $fiber = new Fiber(fn () => null);
+        $fiber->start();
+    }
+};
+
+?>
+--EXPECTF--
+Fatal error: Uncaught FiberError: Cannot switch fibers in current execution context in %sno-switch-dtor-start.php:%d
+Stack trace:
+#0 %sno-switch-dtor-start.php(%d): Fiber->start()
+#1 %sno-switch-dtor-start.php(%d): class@anonymous->__destruct()
+#2 {main}
+  thrown in %sno-switch-dtor-start.php on line %d

Zend/tests/fibers/no-switch-dtor-suspend.phpt

@@ -0,0 +1,24 @@
+--TEST--
+Cannot suspend fiber within destructor
+--FILE--
+<?php
+
+$fiber = new Fiber(function () {
+    $a = new class () {
+        public function __destruct() {
+            Fiber::suspend();
+        }
+    };
+});
+
+$fiber->start();
+
+?>
+--EXPECTF--
+Fatal error: Uncaught FiberError: Cannot switch fibers in current execution context in %sno-switch-dtor-suspend.php:%d
+Stack trace:
+#0 %sno-switch-dtor-suspend.php(%d): Fiber::suspend()
+#1 [internal function]: class@anonymous->__destruct()
+#2 %sno-switch-dtor-suspend.php(%d): Fiber->start()
+#3 {main}
+  thrown in %sno-switch-dtor-suspend.php on line %d

Zend/tests/fibers/no-switch-dtor-throw.phpt

@@ -0,0 +1,30 @@
+--TEST--
+Cannot resume fiber within destructor
+--FILE--
+<?php
+
+$fiber = new Fiber(function () {
+    Fiber::suspend();
+});
+$fiber->start();
+
+return new class ($fiber) {
+    private $fiber;
+
+    public function __construct(Fiber $fiber) {
+        $this->fiber = $fiber;
+    }
+
+    public function __destruct() {
+        $this->fiber->throw(new Error());
+    }
+};
+
+?>
+--EXPECTF--
+Fatal error: Uncaught FiberError: Cannot switch fibers in current execution context in %sno-switch-dtor-throw.php:%d
+Stack trace:
+#0 %sno-switch-dtor-throw.php(%d): Fiber->throw(Object(Error))
+#1 %sno-switch-dtor-throw.php(%d): class@anonymous->__destruct()
+#2 {main}
+  thrown in %sno-switch-dtor-throw.php on line %d

Zend/tests/fibers/no-switch-force-close-finally.phpt

@@ -0,0 +1,31 @@
+--TEST--
+Cannot start a new fiber in a finally block in a force-closed fiber
+--FILE--
+<?php
+
+$fiber = new Fiber(function() {
+    try {
+        Fiber::suspend();
+    } finally {
+        echo "finally\n";
+
+        $fiber = new Fiber(function() {
+            echo "not executed\n";
+        });
+
+        $fiber->start();
+    }
+});
+
+$fiber->start();
+
+?>
+--EXPECTF--
+finally
+
+Fatal error: Uncaught FiberError: Cannot switch fibers in current execution context in %sno-switch-force-close-finally.php:%d
+Stack trace:
+#0 %sno-switch-force-close-finally.php(%d): Fiber->start()
+#1 [internal function]: {closure}()
+#2 {main}
+  thrown in %sno-switch-force-close-finally.php on line %d

Zend/tests/fibers/no-switch-gc.phpt

@@ -0,0 +1,35 @@
+--TEST--
+Context switches are prevented during GC collect cycles
+--FILE--
+<?php
+
+$fiber = new Fiber(function () {
+    call_user_func(function () {
+        $a = new class () {};
+
+        $b = new class () {
+            public function __destruct() {
+                Fiber::suspend();
+            }
+        };
+
+        $a->next = $b;
+        $b->next = $a;
+    });
+
+    gc_collect_cycles();
+});
+
+$fiber->start();
+
+?>
+--EXPECTF--
+Fatal error: Uncaught FiberError: Cannot switch fibers in current execution context in %sno-switch-gc.php:%d
+Stack trace:
+#0 %sno-switch-gc.php(%d): Fiber::suspend()
+#1 [internal function]: class@anonymous->__destruct()
+#2 %sno-switch-gc.php(%d): gc_collect_cycles()
+#3 [internal function]: {closure}()
+#4 %sno-switch-gc.php(%d): Fiber->start()
+#5 {main}
+  thrown in %sno-switch-gc.php on line %d