From: Nikita Popov <nikic@php.net>
Date: Tue, 24 Feb 2015 17:57:14 +0000 (+0100)
Subject: Support list($a, $b) = $a
X-Git-Tag: PRE_PHP7_EREG_MYSQL_REMOVALS~74
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=bdf1430eeba10d444274642572b9e1ac84013080;p=php

Support list($a, $b) = $a

By compiling the RHS $a as a non-CV fetch.

This worked as expected in PHP 5, but broke in PHP 7 due to the
different assign order. However the new implementation is more
general, in that it allows $a on the LHS in any place, not just
the first element.
---

diff --git a/Zend/tests/list_self_assign.phpt b/Zend/tests/list_self_assign.phpt
new file mode 100644
index 0000000000..4640912696
--- /dev/null
+++ b/Zend/tests/list_self_assign.phpt
@@ -0,0 +1,56 @@
+--TEST--
+Test variable occuring on both LHS and RHS of list()
+--FILE--
+<?php
+
+$a = [1, 2, 3];
+list($a, $b, $c) = $a;
+var_dump($a, $b, $c);
+
+$b = [1, 2, 3];
+list($a, $b, $c) = $b;
+var_dump($a, $b, $c);
+
+$c = [1, 2, 3];
+list($a, $b, $c) = $c;
+var_dump($a, $b, $c);
+
+$a = [[1, 2], 3];
+list(list($a, $b), $c) = $a;
+var_dump($a, $b, $c);
+
+$b = [[1, 2], 3];
+list(list($a, $b), $c) = $b;
+var_dump($a, $b, $c);
+
+$b = [1, [2, 3]];
+list($a, list($b, $c)) = $b;
+var_dump($a, $b, $c);
+
+$c = [1, [2, 3]];
+list($a, list($b, $c)) = $c;
+var_dump($a, $b, $c);
+
+?>
+--EXPECT--
+int(1)
+int(2)
+int(3)
+int(1)
+int(2)
+int(3)
+int(1)
+int(2)
+int(3)
+int(1)
+int(2)
+int(3)
+int(1)
+int(2)
+int(3)
+int(1)
+int(2)
+int(3)
+int(1)
+int(2)
+int(3)
diff --git a/Zend/zend_compile.c b/Zend/zend_compile.c
index 9db4f284af..e7177c7cd0 100644
--- a/Zend/zend_compile.c
+++ b/Zend/zend_compile.c
@@ -2316,6 +2316,50 @@ zend_bool zend_is_assign_to_self(zend_ast *var_ast, zend_ast *expr_ast) /* {{{ *
 }
 /* }}} */
 
+/* Detects if list($a, $b, $c) contains variable with given name */
+zend_bool zend_list_has_assign_to(zend_ast *list_ast, zend_string *name) /* {{{ */
+{
+	zend_ast_list *list = zend_ast_get_list(list_ast);
+	uint32_t i;
+	for (i = 0; i < list->children; i++) {
+		zend_ast *var_ast = list->child[i];
+		if (!var_ast) {
+			continue;
+		}
+
+		/* Recursively check nested list()s */
+		if (var_ast->kind == ZEND_AST_LIST && zend_list_has_assign_to(var_ast, name)) {
+			return 1;
+		}
+
+		if (var_ast->kind == ZEND_AST_VAR && var_ast->child[0]->kind == ZEND_AST_ZVAL) {
+			zend_string *var_name = zval_get_string(zend_ast_get_zval(var_ast->child[0]));
+			zend_bool result = zend_string_equals(var_name, name);
+			zend_string_release(var_name);
+			if (result) {
+				return 1;
+			}
+		}
+	}
+
+	return 0;
+}
+/* }}} */
+
+/* Detects patterns like list($a, $b, $c) = $a */
+zend_bool zend_list_has_assign_to_self(zend_ast *list_ast, zend_ast *expr_ast) /* {{{ */
+{
+	/* Only check simple variables on the RHS, as only CVs cause issues with this. */
+	if (expr_ast->kind == ZEND_AST_VAR && expr_ast->child[0]->kind == ZEND_AST_ZVAL) {
+		zend_string *name = zval_get_string(zend_ast_get_zval(expr_ast->child[0]));
+		zend_bool result = zend_list_has_assign_to(list_ast, name);
+		zend_string_release(name);
+		return result;
+	}
+	return 0;
+}
+/* }}} */
+
 void zend_compile_assign(znode *result, zend_ast *ast) /* {{{ */
 {
 	zend_ast *var_ast = ast->child[0];
@@ -2365,7 +2409,13 @@ void zend_compile_assign(znode *result, zend_ast *ast) /* {{{ */
 			zend_emit_op_data(&expr_node);
 			return;
 		case ZEND_AST_LIST:
-			zend_compile_expr(&expr_node, expr_ast);
+			if (zend_list_has_assign_to_self(var_ast, expr_ast)) {
+				/* list($a, $b) = $a should evaluate the right $a first */
+				zend_compile_simple_var_no_cv(&expr_node, expr_ast, BP_VAR_R, 0);
+			} else {
+				zend_compile_expr(&expr_node, expr_ast);
+			}
+
 			zend_compile_list_assign(result, var_ast, &expr_node);
 			return;
 		EMPTY_SWITCH_DEFAULT_CASE();