Bug #78341 [Asn]: Opcache DFA pass over-optimized?

Edit report at https://bugs.php.net/bug.php?id=78341&edit=1 ID: 78341 Updated by: nikic@php.net Reported by: jfcherng at gmail dot com Summary: Opcache DFA pass over-optimized? Status: Assigned Type: Bug Package: opcache Operating System: Win7 x64 PHP Version: 7.3.8RC1 Assigned To: nikic Block user comment: N Private report: N New Comment: Here is a reproducer: <?php function test($a) { // Just some dead code... if (strpos("foo", "foo") !== 0) { echo "Foo"; } $x = $a === null; if ($x) { var_dump($x); } } test(null); Previous Comments: ------------------------------------------------------------------------ [2019-07-29 10:36:29] nikic@php.net We're generating #164.CV30($zvalIsRef) [bool] RANGE[0..1] = IS_NOT_IDENTICAL #162.V36 [any] null JMPZ #164.CV30($zvalIsRef) [bool] RANGE[0..1] BB17 instead of #164.CV30($zvalIsRef) [bool] RANGE[0..1] = IS_NOT_IDENTICAL #162.V36 [any] null NOP JMPZ #164.CV30($zvalIsRef) [bool] RANGE[0..1] BB17 ------------------------------------------------------------------------ [2019-07-28 12:30:18] jfcherng at gmail dot com Line 268: https://github.com/symfony/var-dumper/blob/v4.3.3/Cloner/VarCloner.php#L268 "zvalIsRef" is defined in: https://github.com/symfony/var-dumper/blob/v4.3.3/Cloner/VarCloner.php#L84-L89 ------------------------------------------------------------------------ [2019-07-28 12:26:33] jfcherng at gmail dot com Description: ------------ PHP 7.3.8RC1 (and 7.4snapshot) emits notices after I update symfony/var-dumper to v4.3.3 today. "zvalIsRef in vendor\symfony\var-dumper\Cloner\VarCloner.php on line 268" The variable "zvalIsRef" around VarCloner.php on line 268 is actually obviously defined. So I have much confidence this is a PHP engine's problem. After some tests, this seems to be the problematic commit https://github.com/php/php-src/commit/e7a83ec8dff962ea624508f18b9b10f5add030cc . It's parent 3fa9f9cfae2cedd7b6d26b6487dd156321243ab7 works fine in my test. I am sorry that I am not able to give a smaller test case. Test script: --------------- <?php declare(strict_types=1); // remember to set opcache.enable_cli=1 if this test is done in cli // composer require symfony/var-dumper:v4.3.3 require __DIR__ . '/vendor/autoload.php'; use Symfony\Component\VarDumper\Cloner\VarCloner; $myVar = new ArrayObject(); $cloner = new VarCloner(); $data = $cloner->cloneVar($myVar); Expected result: ---------------- no notice is emitted. Actual result: -------------- Notice: Undefined variable: zvalIsRef in vendor\symfony\var-dumper\Cloner\VarCloner.php on line 268 Notice: Undefined variable: zvalIsRef in vendor\symfony\var-dumper\Cloner\VarCloner.php on line 268 ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=78341&edit=1