Req #72492 [NEW]: optimize copy on write when no actual write is performed

From: youwish dot spambot at nospam dot pls dot example dot org Operating system: Irrelevant PHP version: 7.1.0alpha1 Package: Performance problem Bug Type: Feature/Change Request Bug description:optimize copy on write when no actual write is performed Description: ------------ Not very important, I'm dropping this findings here so they don't get lost in the meanders of web. These operations (and similar ones) don't require a copy to be performed as the result is identical to the original. Test script: --------------- $foo = str_repeat('foo', 100000); var_dump(memory_get_usage()); $baz = '' . $foo; // $baz is identical to $foo var_dump(memory_get_usage()); unset($foo, $baz); echo "\n"; $foo = array_fill(0, 1000, 'foo'); var_dump(memory_get_usage()); $baz = array_merge($foo, []); // $baz is identical to $foo var_dump(memory_get_usage()); unset($foo, $baz); echo "\n"; $foo = array_fill(0, 1000, 'foo'); var_dump(memory_get_usage()); $baz = array_slice($foo, 0); // $baz is identical to $foo var_dump(memory_get_usage()); // etc... -- Edit bug report at https://bugs.php.net/bug.php?id=72492&edit=1 -- Try a snapshot (PHP 5.4): https://bugs.php.net/fix.php?id=72492&r=trysnapshot54 Try a snapshot (PHP 5.5): https://bugs.php.net/fix.php?id=72492&r=trysnapshot55 Try a snapshot (trunk): https://bugs.php.net/fix.php?id=72492&r=trysnapshottrunk Fixed in SVN: https://bugs.php.net/fix.php?id=72492&r=fixed Fixed in release: https://bugs.php.net/fix.php?id=72492&r=alreadyfixed Need backtrace: https://bugs.php.net/fix.php?id=72492&r=needtrace Need Reproduce Script: https://bugs.php.net/fix.php?id=72492&r=needscript Try newer version: https://bugs.php.net/fix.php?id=72492&r=oldversion Not developer issue: https://bugs.php.net/fix.php?id=72492&r=support Expected behavior: https://bugs.php.net/fix.php?id=72492&r=notwrong Not enough info: https://bugs.php.net/fix.php?id=72492&r=notenoughinfo Submitted twice: https://bugs.php.net/fix.php?id=72492&r=submittedtwice register_globals: https://bugs.php.net/fix.php?id=72492&r=globals PHP 4 support discontinued: https://bugs.php.net/fix.php?id=72492&r=php4 Daylight Savings: https://bugs.php.net/fix.php?id=72492&r=dst IIS Stability: https://bugs.php.net/fix.php?id=72492&r=isapi Install GNU Sed: https://bugs.php.net/fix.php?id=72492&r=gnused Floating point limitations: https://bugs.php.net/fix.php?id=72492&r=float No Zend Extensions: https://bugs.php.net/fix.php?id=72492&r=nozend MySQL Configuration Error: https://bugs.php.net/fix.php?id=72492&r=mysqlcfg