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Rewrite $a ?: $b to empty($a) ? $b : $a if $a is a variable #809

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Rewrite $a ?: $b to empty($a) ? $b : $a if $a is a variable #809

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774f60f
Rewrite $a ?: $b to empty($a) ? $b : $a if $a is a variable
hikari-no-yume Sep 5, 2014
9804a72
Use Z_TRY_ADDREF_P to avoid doing horrible things
hikari-no-yume Sep 5, 2014
fa4e37e
Added test
hikari-no-yume Sep 5, 2014
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22 changes: 22 additions & 0 deletions Zend/zend_ast.c
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Original file line number Diff line number Diff line change
Expand Up @@ -342,6 +342,28 @@ ZEND_API void zend_ast_evaluate(zval *result, zend_ast *ast, zend_class_entry *s
}
}

/* addrefs zvals in an AST recursively */
ZEND_API void zend_ast_addref(zend_ast *ast) /* {{{ */
{
if (ast == NULL) {
return;
} else if (ast->kind == ZEND_AST_ZVAL) {
Z_TRY_ADDREF_P(zend_ast_get_zval(ast));
} else if (zend_ast_is_list(ast)) {
zend_ast_list *list = zend_ast_get_list(ast);
uint32_t i;
for (i = 0; i < list->children; i++) {
zend_ast_addref(list->child[i]);
}
} else {
uint32_t i, children = zend_ast_get_num_children(ast);
for (i = 0; i < children; i++) {
zend_ast_addref(ast->child[i]);
}
}
}
/* }}} */

ZEND_API zend_ast *zend_ast_copy(zend_ast *ast)
{
if (ast == NULL) {
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1 change: 1 addition & 0 deletions Zend/zend_ast.h
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Expand Up @@ -200,6 +200,7 @@ ZEND_API zend_ast *zend_ast_list_add(zend_ast *list, zend_ast *op);

ZEND_API void zend_ast_evaluate(zval *result, zend_ast *ast, zend_class_entry *scope TSRMLS_DC);

ZEND_API void zend_ast_addref(zend_ast *ast);
ZEND_API zend_ast *zend_ast_copy(zend_ast *ast);
ZEND_API void zend_ast_destroy(zend_ast *ast);
ZEND_API void zend_ast_destroy_and_free(zend_ast *ast);
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20 changes: 18 additions & 2 deletions Zend/zend_compile.c
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Expand Up @@ -6902,8 +6902,24 @@ void zend_compile_conditional(znode *result, zend_ast *ast TSRMLS_DC) /* {{{ */
uint32_t opnum_jmpz, opnum_jmp, opnum_qm_assign1;

if (!true_ast) {
zend_compile_shorthand_conditional(result, ast TSRMLS_CC);
return;
/* if variable is isset()able, rewrite $a ?: $b to empty($a) ? $b : $a */
if (zend_is_variable(cond_ast) && !zend_is_call(cond_ast))
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Isn't that a behavior change? Before, if $a didn't exist, there were notice, but after, there's no notice anymore.

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A behaviour change, yes, but it doesn't break backwards-compatibility. I'm writing an RFC for this as we speak, just to clarify.

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How does it not break BC? You have no idea what people might do with that notice in their custom error handlers. If you remove it, that code won't be triggered and the app will behave differently.

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Right, it won't break BC for most applications, but it will break things if they relied on it throwing an E_NOTICE. I'll update the RFC to note that.

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OK, I didn't realize that. Within the context of RFC it makes sense. I'd support that for PHP 7.

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It seems a bit inconsistent to me that $a ? $a : $b will throw a notice and $a ?: $b won't. We would need to make that change extremely clear in the documentation highlighting the fact that ?: is now the first operator to suppress these notices and that it is now fundamentally different from its cousin, the ? expr1 : expr2 operator.

{
zend_ast *swap_temp = cond_ast;

cond_ast = ast->child[0] = zend_ast_create(ZEND_AST_EMPTY, cond_ast);

true_ast = ast->child[1] = false_ast;
false_ast = ast->child[2] = swap_temp;

/* avoid any zvals being double-freed due to cond_ast being referenced twice */
zend_ast_addref(swap_temp);
}
else
{
zend_compile_shorthand_conditional(result, ast TSRMLS_CC);
return;
}
}

zend_compile_expr(&cond_node, cond_ast TSRMLS_CC);
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58 changes: 58 additions & 0 deletions tests/lang/operators/shortTernaryIsset.phpt
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@@ -0,0 +1,58 @@
--TEST--
Test short ternary operator for implicit isset cases
--FILE--
<?php

$var = 7;
$var2 = false;

$obj = new StdClass;
$obj->boo = 7;

$arr = [
2 => 7,
"foo" => "bar",
"foobar" => "",
"qux" => $obj,
"bing" => [
"bang"
]
];

var_dump($nonexistant_variable ?: 3);
echo PHP_EOL;
var_dump($var ?: 3);
var_dump($var2 ?: 3);
echo PHP_EOL;
var_dump($obj->boo ?: 3);
var_dump($obj->bing ?: 3);
var_dump($arr["qux"]->boo ?: 3);
var_dump($arr["qux"]->bing ?: 3);
echo PHP_EOL;
var_dump($arr[2] ?: 3);
var_dump($arr["foo"] ?: 3);
var_dump($arr["foobar"] ?: 3);
var_dump($arr["qux"] ?: 3);
var_dump($arr["bing"][0] ?: 3);
var_dump($arr["bing"][1] ?: 3);
?>
--EXPECTF--
int(3)

int(7)
int(3)

int(7)
int(3)
int(7)
int(3)

int(7)
string(3) "bar"
int(3)
object(stdClass)#1 (%d) {
["boo"]=>
int(7)
}
string(4) "bang"
int(3)