Why Do I Get This Segmentation Fault In This PHP Command Line Script?

Question

It's just a quick script to a message to what I call a 'mental log file'. Just to keep track of my thoughts when I drift off and get myself back to work. Anyway, it works alright most of the time, but every so often I get a segmentation fault. Heard of them in C, but never had them before in PHP. Here's the script:

#!/usr/bin/php 
<?php 

    $mental_log_file = "/home/ali/mental-log"; 
    array_shift($argv);      //get rid of the initial arg (name of the command) 
    $log_entry = date('j-n-y H:i') . ' ' . implode(' ', $argv) . "\n";

    file_put_contents($mental_log_file, $log_entry, FILE_APPEND);

Here's what I get on a few runs:

ali@oem-desktop:~$ mlog blah
ali@oem-desktop:~$ mlog blah
Segmentation fault
ali@oem-desktop:~$ mlog blah
ali@oem-desktop:~$ mlog blah
Segmentation fault
ali@oem-desktop:~$ mlog blah
ali@oem-desktop:~$ mlog blah
ali@oem-desktop:~$ mlog blah
Segmentation fault
ali@oem-desktop:~$ mlog blah
ali@oem-desktop:~$ mlog blah
Segmentation fault
ali@oem-desktop:~$ mlog blah
Segmentation fault

Any idea of what I could be doing wrong here? The file seems to be updating correctly as expected even on the runs that produce segmentation faults. I'm running Ubuntu 9.04 Jaunty.

ali@oem-desktop:~$ php --version
PHP 5.2.6-3ubuntu4.1 with Suhosin-Patch 0.9.6.2 (cli) (built: Apr 23 2009 14:37:14) 
Copyright (c) 1997-2008 The PHP Group
Zend Engine v2.2.0, Copyright (c) 1998-2008 Zend Technologies

Thanks in advance.

I have some pretty trivial PHP cli scripts that segfault seemingly at random, too. — JAL
– JAL, Commented Jan 12, 2010 at 2:32

Paul Dixon · Accepted Answer · 2009-07-09 20:25:20Z

9

Try

strace mlog blah

and see if that gives some clues as what it is doing when it dies. For what it's worth, I couldn't reproduce that on a 64 bit Jaunty install with the same php build you report.

edited Jul 9, 2009 at 20:25

answered Jul 9, 2009 at 20:13

Paul Dixon

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4 Comments

Ali Over a year ago

Thanks for that! Tried running it but I'm not so clued up on system calls/low level programming, couldn't really make sense of the output.

Paul Dixon Over a year ago

Paste an strace of a typical crash into pastebin.com and add a link to it in your question

Paul Dixon Over a year ago

Also, troelskn is probably onto something - what extensions have you got enabled?

wired00 Over a year ago

wow... this saved me man... could see it was to do with Autoloading going on... strace is a big help

troelskn · Accepted Answer · 2009-07-09 22:54:06Z

4

It's very likely that you have an extension which somehow messes up. That can happen if the extension was built for a different version of php or of an external library. Try to disable all extensions in php.ini and see if it solves the problem. If it does, then re-enable each extension, one at a time, until you find the offender.

answered Jul 9, 2009 at 22:54

troelskn

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Comments

Fuzzy76 · Accepted Answer · 2009-09-07 11:29:12Z

3

It's probably because of this bug which affects both Ubuntu and Debian... https://bugs.launchpad.net/ubuntu/+source/php5/+bug/343870

answered Sep 7, 2009 at 11:29

Fuzzy76

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Comments

lushin · Accepted Answer · 2009-07-20 14:56:49Z

2

Looks like Ubuntu bug #343870 in php5-mysql. I don't get a segmentation fault any more with PHP mysql and mysqli modules disabled.

answered Jul 20, 2009 at 14:56

lushin

Comments

Evert · Accepted Answer · 2009-07-10 00:30:18Z

1

I've seen the exact same things, and it's usually just in indicator of a PHP bug.

I would upgrade to the latest version, if the problem persists.. file a bug report. If you are stuck to ubuntu versions, you might be able to post a bug report in ubuntu's tracker instead.

answered Jul 10, 2009 at 0:30

Evert

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Comments

Liam Morland · Accepted Answer · 2010-12-02 15:10:40Z

1

Try changing the load order of extension. I had to move pgsql before curl to get rid of a segfault I was having. I tried it after reading this:

http://linux.m2osw.com/php_cli_segmentation_fault_with_pgsql

answered Dec 2, 2010 at 15:10

Liam Morland

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Comments

chaos · Accepted Answer · 2009-07-09 20:18:34Z

0

Unable to replicate, unsurprisingly. Experimentally, I'd try appending to the file using fopen() instead of file_put_contents().

answered Jul 9, 2009 at 20:18

chaos

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h2ooooooo · Accepted Answer · 2013-02-28 14:27:13Z

I got this error due to a simple stack overflow. Why I didn't get another error than a segmentation fault is a good question, but using strace and die() I traced the problem down.

Server

Debian 6.0 (squeeze)

Linux domain.com 2.6.32-5-amd64 #1 SMP Sun Sep 23 10:07:46 UTC 2012 x86_64 GNU/Linux

PHP

PHP 5.3.3-7+squeeze14 with Suhosin-Patch (cli) (built: Aug 6 2012 14:18:06)

Copyright (c) 1997-2009 The PHP Group

Zend Engine v2.3.0, Copyright (c) 1998-2010 Zend Technologies

with Suhosin v0.9.32.1, Copyright (c) 2007-2010, by SektionEins GmbH

Code to reproduce problem

<?php   
    function Bar() {
        return Bar();
    }
    Bar();
?>

Output

php5 overflowtest.php

Segmentation fault

Strace output (in case anyone can use it for anything):

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