How often does it do this? One out of every 3 runs? One out of every 100?

Code coverage hardly runs with PHP-FPM, and usually, through PHP Code Coverage and the PHP CLI. Are you sure PHP-FPM is involved?

As you get a "core dumped", it would be interesting to see what is in the core file. For the MongoDB driver, we use the following to dump the output of core files to see why something would crash:

https://github.com/derickr/mongo-php-driver/blob/master/.travis.yml#L41
and
https://github.com/derickr/mongo-php-driver/blob/master/.travis.scripts/debug-core.sh

Perhaps you can try that to find some more information.

cheers,
Derick

Regarding FPM vs CLI, we're using the FPM version of the offical Docker image (which also includes CLI) also we're generating code coverage with both unit tests in CLI and end to end tests via FPM.

However we found more reproducable case in a different project. Below the most simple version I could reduce it to:

<?php

class Bar
{
public static function baz()
{
return new static();
}
}

function foo(Bar $argumentThatGetsReAssigned)
{
$argumentThatGetsReAssigned = Bar::baz();
non_existing_function();
}

foo(Bar::baz());

This ran in PHP version:

PHP 7.0.27 (cli) (built: Jan 10 2018 03:57:49) ( NTS )
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.0.0, Copyright (c) 1998-2017 Zend Technologies
with Zend OPcache v7.0.27, Copyright (c) 1999-2017, by Zend Technologies
with Xdebug v2.6.0, Copyright (c) 2002-2018, by Derick Rethans

with the following modules:

[PHP Modules]
bcmath
Core
ctype
curl
date
dom
fileinfo
filter
ftp
gd
hash
iconv
imagick
intl
json
libxml
mbstring
mcrypt
mysqli
mysqlnd
openssl
pcntl
pcre
PDO
pdo_mysql
pdo_sqlite
Phar
posix
readline
Reflection
session
SimpleXML
soap
SPL
sqlite3
standard
tokenizer
xdebug
xml
xmlreader
xmlwriter
Zend OPcache
zip
zlib

[Zend Modules]
Xdebug
Zend OPcache

Unfortunately there's no debugging support in the container this code ran in so I can't provide a core file.

Please let me know if I can provide other info.

Thanks,
Lucas

I can reproduce the segfault from the last script, but I can't see why and how this happens yet!

Thanks for looking at it!, I'm curious if we ever find out why this happens :)

Is this issue still relevant to you?

No it isn't since I'm no longer working on this project. thanks for checking!

Let me close this out then. Thanks :-)