core: set zend_pass_function as default constructor

This is to make the semantics of when a class cannot be instiantiated obvious rather than needed to remember to call the get_constructor() handler.

Author: Girgias

Zend/Optimizer/escape_analysis.c

@@ -169,7 +169,7 @@ static bool is_allocation_def(zend_op_array *op_array, zend_ssa *ssa, int def, i
 				 && !ce->create_object
 				 && ce->default_object_handlers->get_constructor == zend_std_get_constructor
 				 && ce->default_object_handlers->dtor_obj == zend_objects_destroy_object
-				 && !ce->constructor
+				 && (!ce->constructor || zend_is_pass_function(ce->constructor))
 				 && !ce->destructor
 				 && !ce->__get
 				 && !ce->__set
@@ -238,7 +238,7 @@ static bool is_local_def(zend_op_array *op_array, zend_ssa *ssa, int def, int va
 				 && !ce->create_object
 				 && ce->default_object_handlers->get_constructor == zend_std_get_constructor
 				 && ce->default_object_handlers->dtor_obj == zend_objects_destroy_object
-				 && !ce->constructor
+				 && (!ce->constructor || zend_is_pass_function(ce->constructor))
 				 && !ce->destructor
 				 && !ce->__get
 				 && !ce->__set

Zend/Optimizer/zend_inference.c

@@ -3395,7 +3395,7 @@ static zend_always_inline zend_result _zend_update_type_info(
 			}
 			/* New objects without constructors cannot escape. */
 			if (ce
-			 && !ce->constructor
+			 && (!ce->constructor || zend_is_pass_function(ce->constructor))
 			 && !ce->create_object
 			 && ce->default_object_handlers->get_constructor == zend_std_get_constructor) {
 				tmp &= ~MAY_BE_RCN;

Zend/zend_builtin_functions.c

@@ -38,6 +38,8 @@ ZEND_MINIT_FUNCTION(core) { /* {{{ */
 	zend_register_default_classes();
 
 	zend_standard_class_def = register_class_stdClass();
+	/* Assign dummy constructor */
+	zend_standard_class_def->constructor = (zend_function*) &zend_pass_function;
 
 	return SUCCESS;
 }

Zend/zend_compile.c

@@ -9351,6 +9351,11 @@ static void zend_compile_class_decl(znode *result, zend_ast *ast, bool toplevel)
 		ce->ce_flags |= ZEND_ACC_TOP_LEVEL;
 	}
 
+	/* Add a default "pass" constructor if none are defined */
+	if (ce->constructor == NULL && (ce->ce_flags & (ZEND_ACC_ENUM|ZEND_ACC_INTERFACE|ZEND_ACC_TRAIT)) == 0) {
+		ce->constructor = (zend_function *) &zend_pass_function;
+	}
+
 	if (ce->__serialize == NULL && zend_hash_exists(&ce->function_table, ZSTR_KNOWN(ZEND_STR_SLEEP))) {
 		zend_error(E_DEPRECATED, "The __sleep() serialization magic method has been deprecated."
 			" Implement __serialize() instead (or in addition, if support for old PHP versions is necessary)");

Zend/zend_compile.h

@@ -634,6 +634,13 @@ struct _zend_execute_data {
 	zend_array          *extra_named_params;
 };
 
+/* export zend_pass_function to allow comparisons against it */
+extern ZEND_API const zend_internal_function zend_pass_function;
+
+static zend_always_inline bool zend_is_pass_function(const zend_function *fn) {
+	return fn == (const zend_function*) &zend_pass_function;
+}
+
 #define ZEND_CALL_HAS_THIS           IS_OBJECT_EX
 
 /* Top 16 bits of Z_TYPE_INFO(EX(This)) are used as call_info flags */

Zend/zend_execute.c

@@ -142,7 +142,7 @@ ZEND_END_ARG_INFO()
 ZEND_API const zend_internal_function zend_pass_function = {
 	ZEND_INTERNAL_FUNCTION, /* type              */
 	{0, 0, 0},              /* arg_flags         */
-	0,                      /* fn_flags          */
+	ZEND_ACC_PUBLIC,                      /* fn_flags          */
 	NULL,                   /* name              */
 	NULL,                   /* scope             */
 	NULL,                   /* prototype         */

Zend/zend_execute.h

@@ -58,9 +58,6 @@ ZEND_API zend_result zend_eval_stringl(const char *str, size_t str_len, zval *re
 ZEND_API zend_result zend_eval_string_ex(const char *str, zval *retval_ptr, const char *string_name, bool handle_exceptions);
 ZEND_API zend_result zend_eval_stringl_ex(const char *str, size_t str_len, zval *retval_ptr, const char *string_name, bool handle_exceptions);
 
-/* export zend_pass_function to allow comparisons against it */
-extern ZEND_API const zend_internal_function zend_pass_function;
-
 ZEND_API ZEND_COLD void ZEND_FASTCALL zend_missing_arg_error(const zend_execute_data *execute_data);
 ZEND_API ZEND_COLD void ZEND_FASTCALL zend_deprecated_function(const zend_function *fbc);
 ZEND_API ZEND_COLD void ZEND_FASTCALL zend_nodiscard_function(const zend_function *fbc);

Zend/zend_inheritance.c

@@ -187,7 +187,7 @@ static void do_inherit_parent_constructor(zend_class_entry *ce) /* {{{ */
 		ce->__debugInfo = parent->__debugInfo;
 	}
 
-	if (ce->constructor) {
+	if (ce->constructor && !zend_is_pass_function(ce->constructor)) {
 		if (parent->constructor && UNEXPECTED(parent->constructor->common.fn_flags & ZEND_ACC_FINAL)) {
 			zend_error_noreturn(E_ERROR, "Cannot override final %s::%s() with %s::%s()",
 				ZSTR_VAL(parent->name), ZSTR_VAL(parent->constructor->common.function_name),

Zend/zend_vm_def.h

@@ -5969,7 +5969,15 @@ ZEND_VM_HANDLER(68, ZEND_NEW, UNUSED|CLASS_FETCH|CONST|VAR, UNUSED|CACHE_SLOT, N
 	}
 
 	constructor = Z_OBJ_HT_P(result)->get_constructor(Z_OBJ_P(result));
-	if (constructor == NULL) {
+	if (UNEXPECTED(constructor == NULL)) {
+		/* No constructor implies that an internal get_constructor was overwritten and threw an exception. */
+		if (UNEXPECTED(!EG(exception))) {
+			zend_throw_error(NULL, "No constructor for %s class", ZSTR_VAL(ce->name));
+		}
+		HANDLE_EXCEPTION();
+	}
+	/* Pass function is special */
+	else if (zend_is_pass_function(constructor)) {
 		/* If there are no arguments, skip over the DO_FCALL opcode. We check if the next
 		 * opcode is DO_FCALL in case EXT instructions are used. */
 		if (EXPECTED(opline->extended_value == 0 && (opline+1)->opcode == ZEND_DO_FCALL)) {
@@ -5982,7 +5990,7 @@ ZEND_VM_HANDLER(68, ZEND_NEW, UNUSED|CLASS_FETCH|CONST|VAR, UNUSED|CACHE_SLOT, N
 
 		/* Perform a dummy function call */
 		call = zend_vm_stack_push_call_frame(
-			ZEND_CALL_FUNCTION, (zend_function *) &zend_pass_function,
+			ZEND_CALL_FUNCTION, constructor,
 			opline->extended_value, NULL);
 	} else {
 		if (EXPECTED(constructor->type == ZEND_USER_FUNCTION) && UNEXPECTED(!RUN_TIME_CACHE(&constructor->op_array))) {