Add consumed_args support for fcall arguments

Author: drealecs

UPGRADING.INTERNALS

@@ -74,6 +74,10 @@ PHP 8.6 INTERNALS UPGRADE NOTES
     longer is a pointer, but a directly embedded HashTable struct.
   . Added a C23_ENUM() helper macro to define forward-compatible fixed-size
     enums.
+  . Added zend_fcall_info.consumed_args together with
+    zend_fci_consumed_arg(), which allows moving a selected callback argument
+    instead of copying it in zend_call_function(). Currently only a single
+    consumed argument is supported.
 
 ========================
 2. Build system changes

Zend/zend_API.c

@@ -4239,6 +4239,7 @@ ZEND_API zend_result zend_fcall_info_init(zval *callable, uint32_t check_flags,
 	fci->param_count = 0;
 	fci->params = NULL;
 	fci->named_params = NULL;
+	fci->consumed_args = 0;
 
 	return SUCCESS;
 }

Zend/zend_API.h

@@ -49,6 +49,7 @@ typedef struct _zend_fcall_info {
 	zval *params;
 	zend_object *object;
 	uint32_t param_count;
+	uint32_t consumed_args;
 	/* This hashtable can also contain positional arguments (with integer keys),
 	 * which will be appended to the normal params[]. This makes it easier to
 	 * integrate APIs like call_user_func_array(). The usual restriction that
@@ -340,6 +341,13 @@ typedef struct _zend_fcall_info_cache {
 #define ZEND_FCI_INITIALIZED(fci) ((fci).size != 0)
 #define ZEND_FCC_INITIALIZED(fcc) ((fcc).function_handler != NULL)
 
+static zend_always_inline uint32_t zend_fci_consumed_arg(uint32_t arg_index) {
+	return arg_index < 32 ? (UINT32_C(1) << arg_index) : UINT32_C(0);
+}
+static zend_always_inline bool zend_fci_is_consumed_arg(uint32_t consumed_args, uint32_t arg_index) {
+	return arg_index < 32 && (consumed_args & (UINT32_C(1) << arg_index));
+}
+
 ZEND_API int zend_next_free_module(void);
 
 BEGIN_EXTERN_C()

Zend/zend_closures.c

@@ -155,6 +155,7 @@ ZEND_METHOD(Closure, call)
 	fci_cache.object = fci.object = newobj;
 
 	fci.size = sizeof(fci);
+	fci.consumed_args = 0;
 	ZVAL_OBJ(&fci.function_name, &closure->std);
 	ZVAL_UNDEF(&closure_result);
 	fci.retval = &closure_result;

Zend/zend_execute_API.c

@@ -797,6 +797,7 @@ zend_result _call_user_function_impl(zval *object, zval *function_name, zval *re
 	fci.param_count = param_count;
 	fci.params = params;
 	fci.named_params = named_params;
+	fci.consumed_args = 0;
 
 	return zend_call_function(&fci, NULL);
 }
@@ -864,6 +865,9 @@ zend_result zend_call_function(zend_fcall_info *fci, zend_fcall_info_cache *fci_
 
 	call = zend_vm_stack_push_call_frame(call_info,
 		func, fci->param_count, object_or_called_scope);
+	uint32_t consumed_args = fci->param_count ? fci->consumed_args : 0;
+
+	ZEND_ASSERT((consumed_args & (consumed_args - 1)) == 0);
 
 	for (uint32_t i = 0; i < fci->param_count; i++) {
 		zval *param = ZEND_CALL_ARG(call, i+1);
@@ -905,7 +909,15 @@ zend_result zend_call_function(zend_fcall_info *fci, zend_fcall_info_cache *fci_
 		}
 
 		if (EXPECTED(!must_wrap)) {
-			ZVAL_COPY(param, arg);
+			if (EXPECTED(consumed_args == 0)
+					|| !zend_fci_is_consumed_arg(consumed_args, i)
+					|| Z_ISREF_P(arg)
+					|| arg != &fci->params[i]) {
+				ZVAL_COPY(param, arg);
+			} else {
+				ZVAL_COPY_VALUE(param, arg);
+				ZVAL_UNDEF(arg);
+			}
 		} else {
 			Z_TRY_ADDREF_P(arg);
 			ZVAL_NEW_REF(param, arg);
@@ -1091,6 +1103,7 @@ ZEND_API void zend_call_known_function(
 	fci.param_count = param_count;
 	fci.params = params;
 	fci.named_params = named_params;
+	fci.consumed_args = 0;
 	ZVAL_UNDEF(&fci.function_name); /* Unused */
 
 	fcic.function_handler = fn;

ext/dom/xpath_callbacks.c

@@ -408,6 +408,7 @@ static zend_result php_dom_xpath_callback_dispatch(php_dom_xpath_callbacks *xpat
 		fci.param_count = param_count;
 		fci.params = params;
 		fci.named_params = NULL;
+		fci.consumed_args = 0;
 		ZVAL_STRINGL(&fci.function_name, function_name, function_name_length);
 
 		zend_call_function(&fci, NULL);

ext/ffi/ffi.c

@@ -950,6 +950,7 @@ static void zend_ffi_callback_trampoline(ffi_cif* cif, void* ret, void** args, v
 	fci.object = NULL;
 	fci.param_count = callback_data->arg_count;
 	fci.named_params = NULL;
+	fci.consumed_args = 0;
 
 	if (callback_data->type->func.args) {
 		int n = 0;

ext/zend_test/test.c

@@ -548,6 +548,61 @@ static ZEND_FUNCTION(zend_call_method_if_exists)
 	}
 }
 
+static ZEND_FUNCTION(zend_test_call_with_consumed_args)
+{
+	zend_fcall_info fci = empty_fcall_info;
+	zend_fcall_info_cache fcc = empty_fcall_info_cache;
+	zval *args;
+	zend_long consumed_args;
+	zval retval;
+	uint32_t actual_consumed_args = 0;
+	uint32_t i;
+	zend_result call_result;
+
+	ZEND_PARSE_PARAMETERS_START(3, 3)
+		Z_PARAM_FUNC(fci, fcc)
+		Z_PARAM_ARRAY(args)
+		Z_PARAM_LONG(consumed_args)
+	ZEND_PARSE_PARAMETERS_END();
+
+	if (UNEXPECTED(consumed_args < 0 || consumed_args > UINT32_MAX)) {
+		zend_argument_value_error(3, "must be between 0 and 4294967295");
+		RETURN_THROWS();
+	}
+
+	zend_fcall_info_args(&fci, args);
+
+	ZVAL_UNDEF(&retval);
+	fci.retval = &retval;
+	fci.consumed_args = (uint32_t) consumed_args;
+
+	call_result = zend_call_function(&fci, &fcc);
+
+	for (i = 0; i < fci.param_count && i < 32; i++) {
+		if (Z_ISUNDEF(fci.params[i])) {
+			actual_consumed_args |= (1u << i);
+		}
+	}
+
+	zend_fcall_info_args_clear(&fci, true);
+
+	if (call_result == FAILURE || EG(exception)) {
+		if (!Z_ISUNDEF(retval)) {
+			zval_ptr_dtor(&retval);
+		}
+		RETURN_THROWS();
+	}
+
+	array_init(return_value);
+	add_assoc_long(return_value, "consumed_args", actual_consumed_args);
+
+	if (Z_ISUNDEF(retval)) {
+		add_assoc_null(return_value, "retval");
+	} else {
+		add_assoc_zval(return_value, "retval", &retval);
+	}
+}
+
 static ZEND_FUNCTION(zend_get_unit_enum)
 {
 	ZEND_PARSE_PARAMETERS_NONE();

ext/zend_test/test.stub.php

@@ -303,6 +303,8 @@ function zend_object_init_with_constructor(string $class, mixed ...$args): mixed
 
     function zend_call_method_if_exists(object $obj, string $method, mixed ...$args): mixed {}
 
+    function zend_test_call_with_consumed_args(callable $cb, array $args, int $consumed_args): array {}
+
     function zend_test_zend_ini_parse_quantity(string $str): int {}
     function zend_test_zend_ini_parse_uquantity(string $str): int {}