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] phi...@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
