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

问题

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.

回答1:

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.

回答2:

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.

回答3:

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

回答4:

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

回答5:

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.

回答6:

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

回答7:

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

回答8:

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):

PASTEBIN LINK

来源：https://stackoverflow.com/questions/1106166/why-do-i-get-this-segmentation-fault-in-this-php-command-line-script

标签

php

segmentation-fault