php crashes with too many objects

Question

Description:

The test script below works fine for 10 iterations but crashes (Segmentation fault) for 400000 iterations while it shouldn't crash.

Uses Php 7.2 on docker (Version 17.09.0-ce-mac35 (19611)) with no extension.

Test script:

<?php
class Lim {
    public $id;
    public $inv;
    public $fi;
    function __construct($id) {
        $this->id = $id;
        $this->inv = new Inv($this);
    }
};

class Inv {
    public $inv;
    public $fi;
    function __construct($inv) { $this->inv = $inv; }
}

$max = 400000;
//$max = 10;

$lim0 = new Lim(0);
$limp = $lim0;
for ($i=1; $i<$max; $i++) {
    $lim = new Lim($i);
    $lim->fi = $limp->inv;
    $limp->inv->fi = $lim;
    $limp = $lim;
}

Does anyone have an idea why ? Thanks

Forbs · Accepted Answer · 2017-12-13 02:44:17Z

2

You are creating a new $lim but not destroying the old one. So you are running out of memory.

add this

unset($lim);

after

$limp = $lim;

answered Dec 13, 2017 at 2:44

Forbs

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4 Comments

HPierce Over a year ago

I'm a little skeptical, but totally open to being proven wrong. I'd expect PHP's garbage collector to address this since $lim is being reassigned on the next iteration. I'd also expect PHP to raise a an "Out of memory" fatal error if memory we an issue - a seg fault is a pretty serious failure.

Forbs Over a year ago

OP is using a docker container so PHP can behave a little differently in there.

Benoit David Over a year ago

The objective is effectively to create 400000 Lim. Php doesn't crash when it gets out of memory ; it just alerts.

Forbs Over a year ago

PHP sure does crash when an OOM occurs. And docker doesn't normally allocate a lot of memory to it when it starts.

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