Segfault when calling a PHP built-in function

[z80maniac]

When an extension calls any built-in PHP function, it crashes, i.e. this code crashes:

Php::call("var_export", "function call");

Note: it only happens when PHP-CPP is built in release mode (with make release).

Full example source code:

#include <phpcpp.h>
#include <iostream>

void myFunction() {
    Php::call("var_export", "function call");
    Php::out << std::endl << "php out" << std::endl;
}

extern "C" PHPCPP_EXPORT void *get_module() {
    static Php::Extension extension("my_extension", "1.0");
    extension.add<myFunction>("myFunction");
    return extension;
}

Build:

g++ -shared -fPIC -o crashtest.so crashtest.cpp -lphpcpp

Test:

php -dextension=./crashtest.so -r 'myFunction();'

Output:

'function call'Segmentation fault (core dumped)

As mentioned above, the crash only happens when PHP-CPP is built in release mode. When PHP-CPP is built in debug mode, the output is as follows:

'function call'
php out

Which is the expected output.

Note: the crash does not happen in Php::out. You can remove it and the extension will still crash. I just added it to check if the test reaches that point in code.

Tested on a clean Ubuntu 18.04 with PHP v7.2.

[scorninpc]

Works fine for me

What did you mean with release and debug mode? -g flag, what?

[z80maniac]

I mean, the PHP-CPP was built with make release, not just make.

[scorninpc]

Same, no problem

release parameter add -02 flag only, nothing more them tell to compiler to optimize the code

[z80maniac]

Here's a fully self-contained example that can be run via Docker:

#!/usr/bin/env bash
set -e
cd "$(dirname -- "$(readlink -f -- "$0")")"

apt update
DEBIAN_FRONTEND=noninteractive apt install -yq php-dev git

mkdir ../build
cd ../build

git clone https://github.com/CopernicaMarketingSoftware/PHP-CPP.git
pushd PHP-CPP && make release && make install && popd

cat << EOF > crashtest.cpp
#include <phpcpp.h>
#include <iostream>

void myFunction() {
    Php::call("var_export", "function call");
    Php::out << std::endl << "php out" << std::endl;
}

extern "C" PHPCPP_EXPORT void *get_module() {
    static Php::Extension extension("my_extension", "1.0");
    extension.add<myFunction>("myFunction");
    return extension;
}
EOF

g++ -shared -fPIC -o crashtest.so crashtest.cpp -lphpcpp

echo "Starting the test..."
php -dextension=./crashtest.so -r 'myFunction();'
echo "The test has been passed."

Name this file run.sh and run Docker in the same directory:

docker run --rm -v"$(pwd)":/test ubuntu:18.04 bash test/run.sh

The last lines will be:

Starting the test...
'function call'test/run.sh: line 33: 10602 Segmentation fault      (core dumped) php -dextension=./crashtest.so -r 'myFunction();'

Now, if you remove the release, the test will be passed correctly:

Starting the test...
'function call'
php out
The test has been passed.

Maybe it's a problem with PHP 7.2 only, and not with PHP 7.3.

[scorninpc]

Yes, can be the 7.2 problem, but as I saw, release only optimize the code, there is no way can be difference.

Sorry for I cannot test docker test

If you see Makefile, you can run in production with "make" only

[z80maniac]

can be the 7.2 problem

In fact, it may be Ubuntu problem. I ran the run.sh against php:7.3.6, php:7.2.19 and php:7.1.30 docker images - and they all passed the test. But when I run it in Ubuntu, it crashes. And the crash is reproducible everywhere: in Docker, in LXC and on my host machine with Kubuntu 19.04.

So, may be it's not a problem in PHP-CPP. Though, I can't say for sure.

there is no way can be difference

There can be a difference if a code is written incorrectly (e.g. produces undefined behavior according to the standard). I encountered this situation many times before in different projects.

Sorry for I cannot test docker test

OK. I just wanted to show that the problem is really not on my side. Instead of Docker, you can try LXC, virtual machine or a live disk - anything that gives you a clean Ubuntu install.

you can run in production with "make" only

As a last resort, yes. But I found out that if PHP-CPP is compiled inside a php:* Docker container, then it can be used to compile extensions that don't crash on Ubuntu. So, there's a semi-decent workaround at least.

[scorninpc]

What the exactly php7.2 version do you have?

[z80maniac]

On my host machine (Kubuntu 19.04):

$ php -v
PHP 7.2.19-0ubuntu0.19.04.1 (cli) (built: Jun  4 2019 14:44:42) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies
    with Zend OPcache v7.2.19-0ubuntu0.19.04.1, Copyright (c) 1999-2018, by Zend Technologies

In LXC and Docker containers (Ubuntu 18.04):

# php -v
PHP 7.2.19-0ubuntu0.18.04.1 (cli) (built: Jun  4 2019 14:48:12) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies
    with Zend OPcache v7.2.19-0ubuntu0.18.04.1, Copyright (c) 1999-2018, by Zend Technologies

However, as I said earlier, the test is passed successfully on php:7.2.19 Docker image, which is Debian-based (Stretch).