[PHP-DEV] How to track down an APC bug

The goal of this message is to encourage and motivate a few people to
give me a hand with tracking down APC bugs. There are still a few
outstanding bugs that is slowing PHP 5.4 adoption and it would be really
nice to plow through these instead of wasting cycles on some of the
other discussions going on here.

The example bug I will use is one I just fixed. Bug http://php.net/62398
which was that with apc.stat=0 the second request (eg. the cached
request) to a certain script would have include filenames replaced with
an empty string.

Clue #1 here is that we are dealing with string literals and those
obviously changed a lot in 5.4.

Clue #2 I got lucky with. I was able to reproduce it locally which makes
everything much simpler because then Valgrind can do most of the
thinking for us.

So, knowing it has to do with string literals and taking my reproduce
case, I first eliminated all non-php code by using the built-in web
server in 5.4. I have a little memcheck shell script that runs Valgrind
with my preferred options. It looks like this:

#!/bin/bash
USE_ZEND_ALLOC=0 valgrind --tool=memcheck
--suppressions=/home/rasmus/.suppressions --leak-check=yes
--track-origins=yes --num-callers
=30 --show-reachable=yes "$ <at> "

And my .suppressions file can be found here: