Move fiber stack allocation within try

If VM stack allocation fails, the bailout will be caught within the fiber.

Author: trowski

Zend/tests/fibers/out-of-memory-in-recursive-fiber.phpt

@@ -0,0 +1,26 @@
+--TEST--
+Out of Memory from recursive fiber creation
+--INI--
+memory_limit=10K
+--SKIPIF--
+<?php
+if (getenv("USE_ZEND_ALLOC") === "0") {
+    die("skip Zend MM disabled");
+}
+?>
+--FILE--
+<?php
+
+function create_fiber(): Fiber
+{
+    $fiber = new Fiber('create_fiber');
+    $fiber->start();
+    return $fiber;
+}
+
+$fiber = new Fiber('create_fiber');
+$fiber->start();
+
+?>
+--EXPECTF--
+Fatal error: Allowed memory size of %d bytes exhausted%s(tried to allocate %d bytes) in %sout-of-memory-in-recursive-fiber.php on line %d

Zend/zend_fibers.c

@@ -336,29 +336,31 @@ static void ZEND_STACK_ALIGNED zend_fiber_execute(zend_fiber_context *context)
 		error_reporting = E_ALL;
 	}
 
-	zend_vm_stack stack = zend_fiber_vm_stack_alloc(ZEND_FIBER_VM_STACK_SIZE);
-	EG(vm_stack) = stack;
-	EG(vm_stack_top) = stack->top + ZEND_CALL_FRAME_SLOT;
-	EG(vm_stack_end) = stack->end;
-	EG(vm_stack_page_size) = ZEND_FIBER_VM_STACK_SIZE;
+	EG(vm_stack) = NULL;
 
-	fiber->execute_data = (zend_execute_data *) stack->top;
-	fiber->stack_bottom = fiber->execute_data;
+	zend_first_try {
+		zend_vm_stack stack = zend_fiber_vm_stack_alloc(ZEND_FIBER_VM_STACK_SIZE);
+		EG(vm_stack) = stack;
+		EG(vm_stack_top) = stack->top + ZEND_CALL_FRAME_SLOT;
+		EG(vm_stack_end) = stack->end;
+		EG(vm_stack_page_size) = ZEND_FIBER_VM_STACK_SIZE;
 
-	memset(fiber->execute_data, 0, sizeof(zend_execute_data));
+		fiber->execute_data = (zend_execute_data *) stack->top;
+		fiber->stack_bottom = fiber->execute_data;
 
-	fiber->execute_data->func = &zend_fiber_function;
-	fiber->stack_bottom->prev_execute_data = EG(current_execute_data);
+		memset(fiber->execute_data, 0, sizeof(zend_execute_data));
 
-	EG(current_execute_data) = fiber->execute_data;
-	EG(jit_trace_num) = 0;
-	EG(error_reporting) = error_reporting;
+		fiber->execute_data->func = &zend_fiber_function;
+		fiber->stack_bottom->prev_execute_data = EG(current_execute_data);
 
-	fiber->fci.retval = &fiber->value;
+		EG(current_execute_data) = fiber->execute_data;
+		EG(jit_trace_num) = 0;
+		EG(error_reporting) = error_reporting;
 
-	fiber->status = ZEND_FIBER_STATUS_RUNNING;
+		fiber->fci.retval = &fiber->value;
+
+		fiber->status = ZEND_FIBER_STATUS_RUNNING;
 
-	zend_first_try {
 		zend_call_function(&fiber->fci, &fiber->fci_cache);
 
 		zval_ptr_dtor(&fiber->fci.function_name);