Implement explicit send-by-ref

Zend/Optimizer/optimize_func_calls.c

@@ -340,6 +340,13 @@ void zend_optimize_func_calls(zend_op_array *op_array, zend_optimizer_ctx *ctx)
 					break;
 				}
 				break;
+			case ZEND_SEND_EXPLICIT_REF:
+				if (call_stack[call - 1].func) {
+					if (ARG_SHOULD_BE_SENT_BY_REF(call_stack[call - 1].func, opline->op2.num)) {
+						opline->opcode = ZEND_SEND_REF;
+					}
+				}
+				break;
 			case ZEND_SEND_UNPACK:
 			case ZEND_SEND_USER:
 			case ZEND_SEND_ARRAY:

Zend/Optimizer/sccp.c

@@ -238,6 +238,8 @@ static bool can_replace_op1(
 		case ZEND_UNSET_DIM:
 		case ZEND_UNSET_OBJ:
 		case ZEND_SEND_REF:
+		case ZEND_SEND_EXPLICIT_REF:
+		case ZEND_SEND_EXPLICIT_REF_FUNC:
 		case ZEND_SEND_VAR_EX:
 		case ZEND_SEND_FUNC_ARG:
 		case ZEND_SEND_UNPACK:

Zend/Optimizer/zend_call_graph.c

@@ -139,6 +139,8 @@ ZEND_API void zend_analyze_calls(zend_arena **arena, zend_script *script, uint32
 			case ZEND_SEND_VAR_EX:
 			case ZEND_SEND_FUNC_ARG:
 			case ZEND_SEND_REF:
+			case ZEND_SEND_EXPLICIT_REF:
+			case ZEND_SEND_EXPLICIT_REF_FUNC:
 			case ZEND_SEND_VAR_NO_REF:
 			case ZEND_SEND_VAR_NO_REF_EX:
 			case ZEND_SEND_USER:

Zend/Optimizer/zend_dfg.c

@@ -154,6 +154,7 @@ static zend_always_inline void _zend_dfg_add_use_def_op(const zend_op_array *op_
 		case ZEND_BIND_INIT_STATIC_OR_JMP:
 		case ZEND_SEND_VAR_NO_REF:
 		case ZEND_SEND_VAR_NO_REF_EX:
+		case ZEND_SEND_EXPLICIT_REF:
 		case ZEND_SEND_VAR_EX:
 		case ZEND_SEND_FUNC_ARG:
 		case ZEND_SEND_REF:

Zend/Optimizer/zend_inference.c

@@ -3268,6 +3268,7 @@ static zend_always_inline zend_result _zend_update_type_info(
 			}
 			break;
 		case ZEND_SEND_REF:
+		case ZEND_SEND_EXPLICIT_REF:
 			if (ssa_op->op1_def >= 0) {
 				tmp = MAY_BE_REF|MAY_BE_RC1|MAY_BE_RCN|MAY_BE_ANY|MAY_BE_ARRAY_KEY_ANY|MAY_BE_ARRAY_OF_ANY|MAY_BE_ARRAY_OF_REF;
 				UPDATE_SSA_TYPE(tmp, ssa_op->op1_def);
@@ -3658,6 +3659,7 @@ static zend_always_inline zend_result _zend_update_type_info(
 							case ZEND_SEND_VAR_NO_REF:
 							case ZEND_SEND_VAR_NO_REF_EX:
 							case ZEND_SEND_REF:
+							case ZEND_SEND_EXPLICIT_REF:
 							case ZEND_ASSIGN_REF:
 							case ZEND_YIELD:
 							case ZEND_INIT_ARRAY:
@@ -4930,6 +4932,7 @@ ZEND_API bool zend_may_throw_ex(const zend_op *opline, const zend_ssa_op *ssa_op
 				case ZEND_FETCH_DIM_IS:
 				case ZEND_FETCH_OBJ_IS:
 				case ZEND_SEND_REF:
+				case ZEND_SEND_EXPLICIT_REF:
 				case ZEND_UNSET_CV:
 				case ZEND_ISSET_ISEMPTY_CV:
 				case ZEND_MAKE_REF:
@@ -4958,6 +4961,7 @@ ZEND_API bool zend_may_throw_ex(const zend_op *opline, const zend_ssa_op *ssa_op
 				case ZEND_SEND_VAR_NO_REF:
 				case ZEND_SEND_VAR_NO_REF_EX:
 				case ZEND_SEND_REF:
+				case ZEND_SEND_EXPLICIT_REF:
 				case ZEND_SEPARATE:
 				case ZEND_END_SILENCE:
 				case ZEND_MAKE_REF:

Zend/Optimizer/zend_ssa.c

@@ -685,6 +685,7 @@ static zend_always_inline int _zend_ssa_rename_op(const zend_op_array *op_array,
 		case ZEND_SEND_VAR_EX:
 		case ZEND_SEND_FUNC_ARG:
 		case ZEND_SEND_REF:
+		case ZEND_SEND_EXPLICIT_REF:
 		case ZEND_SEND_UNPACK:
 		case ZEND_FE_RESET_RW:
 		case ZEND_MAKE_REF:

Zend/tests/explicitSendByRef/__call.phpt

@@ -0,0 +1,40 @@
+--TEST--
+__call() magic with explicit pass by ref
+--FILE--
+<?php
+
+class Incrementor {
+    public function inc(&$i) {
+        $i++;
+    }
+}
+
+class ForwardCalls {
+    private $object;
+    public function __construct($object) {
+        $this->object = $object;
+    }
+    public function __call(string $method, array $args) {
+        return $this->object->$method(...$args);
+    }
+}
+
+$forward = new ForwardCalls(new Incrementor);
+
+$i = 0;
+try {
+    $forward->inc(&$i);
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+var_dump($i);
+
+$i = 0;
+$forward->inc($i);
+var_dump($i);
+
+?>
+--EXPECT--
+Cannot pass reference to by-value parameter 1
+int(0)
+int(0)

Zend/tests/explicitSendByRef/basic.phpt

@@ -0,0 +1,86 @@
+--TEST--
+Basic tests for explicit pass-by-ref
+--FILE--
+<?php
+
+// Works (by-ref arg)
+$a = 42;
+incArgRef(&$a);
+var_dump($a);
+
+// Works (by-ref arg, deep reference)
+writeArgRef(&$b[0][1]);
+var_dump($b);
+
+// Works (prefer-ref arg)
+$c = 42;
+$vars = ['b' => 2, 'a' => 1];
+$vars2 = [2, 1];
+array_multisort(&$vars, $vars2);
+var_dump($vars, $vars2);
+
+// Works (by-ref arg, by-ref function)
+$e = 42;
+incArgRef(&returnsRef($e));
+var_dump($e);
+
+// Fails (by-val arg)
+try {
+    $f = 1;
+    var_dump(incArgVal(&$f));
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
+// Fails (by-ref arg, by-val function)
+try {
+    $g = 42;
+    incArgRef(&returnsVal($g));
+    var_dump($g);
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
+// Fails (by-val arg, by-ref function)
+try {
+    $h = 1;
+    var_dump(incArgVal(&returnsRef($h)));
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
+// Functions intentionally declared at the end of the file,
+// to avoid the fbc being known during compilation
+function incArgVal($a) { return $a + 1; }
+function incArgRef(&$a) { $a++; }
+function writeArgRef(&$a) { $a = 43; }
+
+function returnsVal($a) { return $a; }
+function &returnsRef(&$a) { return $a; }
+
+?>
+--EXPECT--
+int(43)
+array(1) {
+  [0]=>
+  array(1) {
+    [1]=>
+    int(43)
+  }
+}
+array(2) {
+  ["a"]=>
+  int(1)
+  ["b"]=>
+  int(2)
+}
+array(2) {
+  [0]=>
+  int(1)
+  [1]=>
+  int(2)
+}
+int(43)
+Cannot pass reference to by-value parameter 1
+Cannot pass result of by-value function by reference
+Cannot pass reference to by-value parameter 1

Zend/tests/explicitSendByRef/call_user_func.phpt

@@ -0,0 +1,14 @@
+--TEST--
+call_user_func() with explicit pass by ref
+--FILE--
+<?php
+
+function inc(&$i) { $i++; }
+
+$i = 0;
+call_user_func('Foo\inc', &$i);
+var_dump($i);
+
+?>
+--EXPECTF--
+Fatal error: Cannot pass reference to by-value parameter 2 in %s on line %d

Zend/tests/explicitSendByRef/compileError.phpt

@@ -0,0 +1,11 @@
+--TEST--
+A compilation error is thrown is the ref/val mismatch is detected at compile-time
+--FILE--
+<?php
+
+function argByVal($a) {}
+argByVal(&$b);
+
+?>
+--EXPECTF--
+Fatal error: Cannot pass reference to by-value parameter 1 in %s on line %d

Zend/tests/explicitSendByRef/compileErrorForOptimizedFunction.phpt

@@ -0,0 +1,12 @@
+--TEST--
+A compilation error is thrown when passing result of optimized function by explicit ref
+--FILE--
+<?php
+
+function argByRef(&$a) {}
+
+argByRef(&strlen("foo"));
+
+?>
+--EXPECTF--
+Fatal error: Cannot pass result of by-value function by reference in %s on line %d

Zend/tests/explicitSendByRef/manyArgs.phpt

@@ -0,0 +1,52 @@
+--TEST--
+Test behavior with many args (slow-path)
+--FILE--
+<?php
+
+$a = 42;
+argByRef(
+    100, 101, 102, 103, 104, 105, 106, 107, 108, 109,
+    110, 111, 112, 113, 114, 115, 116, 117, 118, 119,
+    120, 121, 122, 123, 124, 125, 126, 127, 128, 129,
+    130, 131, 132, 133, 134, 135, 136, 137, 138, 139,
+    &$a
+);
+var_dump($a);
+
+try {
+    $b = 42;
+    argByVal(
+        100, 101, 102, 103, 104, 105, 106, 107, 108, 109,
+        110, 111, 112, 113, 114, 115, 116, 117, 118, 119,
+        120, 121, 122, 123, 124, 125, 126, 127, 128, 129,
+        130, 131, 132, 133, 134, 135, 136, 137, 138, 139,
+        &$a
+    );
+    var_dump($b);
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
+function argByVal(
+    $a00, $a01, $a02, $a03, $a04, $a05, $a06, $a07, $a08, $a09,
+    $a10, $a11, $a12, $a13, $a14, $a15, $a16, $a17, $a18, $a19,
+    $a20, $a21, $a22, $a23, $a24, $a25, $a26, $a27, $a28, $a29,
+    $a30, $a31, $a32, $a33, $a34, $a35, $a36, $a37, $a38, $a39,
+    $val
+) {
+    return $val + 1;
+}
+function argByRef(
+    $a00, $a01, $a02, $a03, $a04, $a05, $a06, $a07, $a08, $a09,
+    $a10, $a11, $a12, $a13, $a14, $a15, $a16, $a17, $a18, $a19,
+    $a20, $a21, $a22, $a23, $a24, $a25, $a26, $a27, $a28, $a29,
+    $a30, $a31, $a32, $a33, $a34, $a35, $a36, $a37, $a38, $a39,
+    &$ref
+) {
+    $ref++;
+}
+
+?>
+--EXPECT--
+int(43)
+Cannot pass reference to by-value parameter 41

Zend/tests/explicitSendByRef/parseErrorOnNonVariable.phpt

@@ -0,0 +1,11 @@
+--TEST--
+Using explicit pass-by-ref with a non-variable results in a parse error
+--FILE--
+<?php
+
+function byRef(&$a) {}
+byRef(&null);
+
+?>
+--EXPECTF--
+Parse error: syntax error, unexpected token ")", expecting "->" or "?->" or "{" or "[" in %s on line %d

Zend/zend_compile.c

@@ -3747,9 +3747,30 @@ static uint32_t zend_compile_args(
 			arg_count++;
 		}
 
-		/* Treat passing of $GLOBALS the same as passing a call.
-		 * This will error at runtime if the argument is by-ref. */
-		if (zend_is_call(arg) || is_globals_fetch(arg)) {
+		if (arg->kind == ZEND_AST_REF) {
+			arg = arg->child[0];
+			ZEND_ASSERT(zend_is_variable_or_call(arg));
+
+			if (fbc && !ARG_SHOULD_BE_SENT_BY_REF(fbc, arg_num)) {
+				zend_error_noreturn(E_COMPILE_ERROR,
+					"Cannot pass reference to by-value parameter %" PRIu32, arg_num);
+			}
+
+			zend_compile_var(&arg_node, arg, BP_VAR_W, 1);
+			if (zend_is_call(arg)) {
+				if (arg_node.op_type & (IS_CONST|IS_TMP_VAR)) {
+					/* Function call was converted into builtin instruction */
+					zend_error_noreturn(E_COMPILE_ERROR,
+						"Cannot pass result of by-value function by reference");
+				}
+
+				opcode = ZEND_SEND_EXPLICIT_REF_FUNC;
+			} else {
+				opcode = fbc ? ZEND_SEND_REF : ZEND_SEND_EXPLICIT_REF;
+			}
+		} else if (zend_is_call(arg) || is_globals_fetch(arg)) {
+			/* Treat passing of $GLOBALS the same as passing a call.
+			 * This will error at runtime if the argument is by-ref. */
 			zend_compile_var(&arg_node, arg, BP_VAR_R, 0);
 			if (arg_node.op_type & (IS_CONST|IS_TMP_VAR)) {
 				/* Function call was converted into builtin instruction */
@@ -4281,6 +4302,10 @@ static zend_result zend_compile_func_cuf(znode *result, zend_ast_list *args, zen
 		znode arg_node;
 		zend_op *opline;
 
+		if (arg_ast->kind == ZEND_AST_REF) {
+			zend_error_noreturn(E_COMPILE_ERROR,
+				"Cannot pass reference to by-value parameter %" PRIu32, i + 1);
+		}
 		zend_compile_expr(&arg_node, arg_ast);
 
 		opline = zend_emit_op(NULL, ZEND_SEND_USER, &arg_node, NULL);

Zend/zend_execute.c

@@ -4394,6 +4394,8 @@ static void cleanup_unfinished_calls(zend_execute_data *execute_data, uint32_t o
 					case ZEND_SEND_VAR_NO_REF:
 					case ZEND_SEND_VAR_NO_REF_EX:
 					case ZEND_SEND_USER:
+					case ZEND_SEND_EXPLICIT_REF:
+					case ZEND_SEND_EXPLICIT_REF_FUNC:
 						if (level == 0) {
 							/* For named args, the number of arguments is up to date. */
 							if (opline->op2_type != IS_CONST) {

Zend/zend_language_parser.y

@@ -904,6 +904,7 @@ argument:
 	|	identifier ':' expr
 			{ $$ = zend_ast_create(ZEND_AST_NAMED_ARG, $1, $3); }
 	|	T_ELLIPSIS expr	{ $$ = zend_ast_create(ZEND_AST_UNPACK, $2); }
+	|	ampersand variable	{ $$ = zend_ast_create(ZEND_AST_REF, $2); }
 ;
 
 global_var_list: