php 5.5 memory leak when using "continue 2" inside two foreach loops?

Question

I just came across a strange memory leak issue. I managed to track the problem down to the following code:

<?php
$data=array();
for($c=0; $c<32768; $c++)
    $data[$c]=array(1, 2, 3);
$filter=array(1, 2, 3);

for($kc=0; $kc<25600; $kc++)
{
    $cm=memory_get_usage(true);
    $pm=memory_get_peak_usage(true);
    echo "<b>loop $kc: current_memory: $cm, peak_memory: $pm...</b><br>";
    flush();

    foreach($data as $entry)
        foreach($filter as $pattern)
            continue 2;
}
?>

Output:

loop 0: current_memory: 12582912, peak_memory: 12582912...
loop 1: current_memory: 20709376, peak_memory: 20709376...
loop 2: current_memory: 28835840, peak_memory: 28835840...
loop 3: current_memory: 36962304, peak_memory: 36962304...
loop 4: current_memory: 45088768, peak_memory: 45088768...
loop 5: current_memory: 53215232, peak_memory: 53215232...
loop 6: current_memory: 61341696, peak_memory: 61341696...
loop 7: current_memory: 69468160, peak_memory: 69468160...
loop 8: current_memory: 77594624, peak_memory: 77594624...
loop 9: current_memory: 85721088, peak_memory: 85721088...
loop 10: current_memory: 93847552, peak_memory: 93847552...
loop 11: current_memory: 101974016, peak_memory: 101974016...
loop 12: current_memory: 110100480, peak_memory: 110100480...
loop 13: current_memory: 118226944, peak_memory: 118226944...
loop 14: current_memory: 126353408, peak_memory: 126353408...
loop 15: current_memory: 134479872, peak_memory: 134479872...
loop 16: current_memory: 142606336, peak_memory: 142606336...
loop 17: current_memory: 151257088, peak_memory: 151257088...
loop 18: current_memory: 159383552, peak_memory: 159383552...
loop 19: current_memory: 167510016, peak_memory: 167510016...
loop 20: current_memory: 175636480, peak_memory: 175636480...
loop 21: current_memory: 183762944, peak_memory: 183762944...
loop 22: current_memory: 191889408, peak_memory: 191889408...
loop 23: current_memory: 200015872, peak_memory: 200015872...
loop 24: current_memory: 208142336, peak_memory: 208142336...
loop 25: current_memory: 216268800, peak_memory: 216268800...
loop 26: current_memory: 224395264, peak_memory: 224395264...
loop 27: current_memory: 232521728, peak_memory: 232521728...
loop 28: current_memory: 240648192, peak_memory: 240648192...
loop 29: current_memory: 248774656, peak_memory: 248774656...
loop 30: current_memory: 256901120, peak_memory: 256901120...
loop 31: current_memory: 265027584, peak_memory: 265027584...
Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 40 bytes) in xxx

When I remove the "continue 2" statement and use a simple "break" or "continue", the memory usage stays constant. Can anyone confirm this strange behavior? Did I find a memory leak bug in php 5.5? Using php-cli doesn't show this strange behavior. Only using php as mod_php inside apache shows this behavior.

My System:

$ php --version
PHP 5.5.11-2 (cli) (built: Apr  8 2014 11:42:22) 
Copyright (c) 1997-2014 The PHP Group
Zend Engine v2.5.0, Copyright (c) 1998-2014 Zend Technologies
    with Zend OPcache v7.0.4-dev, Copyright (c) 1999-2014, by Zend Technologies

$ apache2ctl status
Apache Server Status for localhost (via ::1)

   Server Version: Apache/2.4.9 (Debian)
          mod_fastcgi/mod_fastcgi-SNAP-0910052141 PHP/5.5.11-2
          mod_perl/2.0.8 Perl/v5.18.2

   Server MPM: prefork
   Server Built: Mar 29 2014 21:52:01

I'm on current Debian testing (Jessie).

Thanks for your help!

Answer 1

WAIT !!

You should not disable opcache: as well as caching, opcache performs optimization.

Optimization means that opcache changes the compiled opcodes.

I am certain that it is the case that tuning optimization will show you where the bug is introduced, this will mean you can create a bug report at bugs.php.net and we have a chance of fixing the problem for everyone.

Please take the time to do this, please.

Tuning Optimization

Opcache has several optimization passes, https://gist.github.com/krakjoe/962e54c38b155f896b00

Configuring which passes run is a matter of changing opcache.optimization_level in your configuration, this is a bitmask, by default 0xffffffff.

If you need help debugging visit #php.pecl on EFnet.

Note: to have opcache enabled in php-cli, change opcache.enable_cli to 1, this will allow you to test in console, the same behaviour should display itself

Answer 2

Just for the record the "continue 2" bug is verified still under 5.5 and 5.6.3 (https://bugs.php.net/bug.php?id=65743). One work around is to utilize the 'goto-hack' and not continue but go 'back' to a defined label in the first foreach... i know, f*gly but works (with opcache)