PHP 7.3 segfaults when forking and using preg_match

[ruudk]

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Problem

There seems to be an issue with PHP 7.3 10.14.2 (18C54) on Mojave. The issue was discovered by @bobthecow.

How to reproduce

• brew install [email protected]
• Create test.php with the following contents:

<?php
if (preg_match('/./', 'a')) echo "pre-fork works\n";
$pid = pcntl_fork();
if ($pid == -1) {
    die('fail');
} elseif ($pid) {
    if (preg_match('/./', 'a')) echo "parent works\n";
    pcntl_wait($status);
    if (pcntl_wifsignaled($status) && pcntl_wtermsig($status) == SIGSEGV) {
        die('child process segfaulted');
    }
} else {
    if (preg_match('/./', 'a')) echo "child works\n";
}

• Run it with /usr/local/opt/[email protected]/bin/php test.php

Expected output:

pre-fork works
parent works
child works

But on Homebrew with PHP 7.3.0 on Mojave 10.14.2 (18C54) it shows:

pre-fork works
parent works
child process segfaulted

The issue does not happen on Ubuntu 16.04 + PHP 7.3 (ppa:ondre/php) for example.

[fxcoudert]

Can you give us a backtrace of the segfault? Either by attaching a debugger, or looking up the macOS crash log for the process?

[ruudk]

@fxcoudert Sure, you can find the crash report here

[fxcoudert]

From the crash log, it appears to be the bug reported here: https://bugs.php.net/bug.php?id=77260

[ruudk]

@fxcoudert It looks really the same indeed. Also this:

I did not experience this issue on production servers running Debian and PHP 7.3 from sury.

So I guess we have to wait for PHP to fix this. Do you want to close this here?

[fxcoudert]

Yes, I don't think there is much we can do here. We'll have to wait that PHP fixes this. Thanks for the bug report @ruudk!

[SMillerDev]

maybe #35660 had something to do with it.

[ruudk]

@SMillerDev Makes sense, can you test out the script above and see if it segfaults on your #35660 branch?

[SMillerDev]

It's already merged. Doesn't seem fixed though :(

[Alexia]

Temporary workaround is to set this in your php.ini:
pcre.jit=0