Req #52173 [Com]: ext/pcntl doesn't store/report errors
Edit report at http://bugs.php.net/bug.php?id=52173&edit=1
ID: 52173
Comment by: nick dot telford at gmail dot com
Reported by: nick dot telford at gmail dot com
Summary: ext/pcntl doesn't store/report errors
Status: Open
Type: Feature/Change Request
Package: PCNTL related
Operating System: Linux
PHP Version: trunk-SVN-2010-06-24 (SVN)
New Comment:
I've attached a patch that implements solution #3.
The patch used the extent of my amazing copy/paste skills to extract the
posix_get_last_error() and posix_strerror() functionality from ext/posix
and
duplicate it in ext/pcntl.
If there's anything wrong with this patch, please let me know. But let
me down
lately - this is the first time I've written (if you can call it that)
any C,
let alone worked on a PHP extension. We've all gotta start somewhere :)
If you need me to write tests etc. please let me know, also any tips on
how to
go about doing so.
I've tested this using the example in the description and it works a
treat.
Previous Comments:
------------------------------------------------------------------------
[2010-06-24 18:19:05] philip@php.net
I like option #3.
------------------------------------------------------------------------
[2010-06-24 16:58:59] nick dot telford at gmail dot com
Minor addendum: A solid use-case as to why it is useful for the userland
code to
read the error code.
When calling pcntl_wait(), -1 will be returned if there are no child
processes
running (errno == ECHILD) and also if the call is interrupted by a
signal (errno
== EINTR).
This makes determining whether there are children left to wait on
tricky, as -1
could simply be an interrupt from a signal being handled.
------------------------------------------------------------------------
[2010-06-24 16:40:37] nick dot telford at gmail dot com
Description:
------------
The following ext/pcntl extensions "return -1 on failure", yet have
multiple
possible reasons for failure: pcntl_fork, pcntl_wait, pcntl_waitpid
Each of these functions can fail for several reasons and in some cases
(especially wait/waitpid) it is useful for the userland code to be able
to
handle the different error codes.
The Linux man pages for fork(2) and wait/waitpid(2) all specify that the
error
code is stored in "errno" when an error occurs. I only have experience
of the
System V (Linux) way, so I'm not sure if this is interoperable, although
I
believe so.
The ext/posix function posix_get_last_error() states that it returns the
error
code for the last posix function that failed. Internally, all of these
functions
also use "errno" to store the error code, but explicitly copy that to
another
variable, which posix_get_last_error() returns
(http://lxr.php.net/opengrok/xref/PHP_5_2/ext/posix/posix.c#1167)
I see two possible solutions, either:
- posix_get_last_error() should be used to return these errors.
Although this
would add a dependency between the two extensions.
- An optional parameter, &$errno, should be added to pcntl_fork(),
pcntl_wait()
and pcntl_waitpid() that is populated with errno if the result is -1.
- A function is added to ext/pcntl, pcntl_get_last_error(), that
operates in a
similar way to posix_get_last_error().
The third option seems simplest and most compatible, although I can't
help but
feel these two extensions really belong together as one big happy
family. What's
the reason they're separate in the first place?
Test script:
---------------
<?php
$pid = pcntl_wait($s);
var_dump($pid, posix_get_last_error());
Expected result:
----------------
int(-1)
int(10) # ECHILD
Actual result:
--------------
int(-1)
int(0)
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/bug.php?id=52173&edit=1
Thread (5 messages)