PHP extension not built with same debug and thread safe as PHP

Its hard to say what exactly was going wrong, I can only say that the extension was build using a different config than the php version.

I will describe some reproducible steps how to compile a most basic extension with debug symbols within the PHP source folder. The extension contains no code except of some boilerplate code created by ext_skel. It just describes the compilation process on UNIX. It is a shell script, you might execute it.

#!/bin/sh

# Should work for all PHP5 versions
VERSION="5.6.9"

# Download the PHP source code
wget \
    --continue "http://de2.php.net/get/php-$VERSION.tar.gz/from/this/mirror" \
    -O "php-$VERSION".tar.gz

tar xf "php-$VERSION.tar.gz" && cd "php-$VERSION/ext"

# Create a hello extension from skeletons
./ext_skel --extname="hello"

# Uncomment two lines in ext/hello/config.m4
# Read the comments there and you'll know what I'm doing
sed -ri.original \
    -e 's/(dnl )(PHP_ARG_ENABLE\(hello)/\2/' \
    -e 's/(dnl )(\[  --enable-hello)/\2/' \
    hello/config.m4

# Build PHP and the extension
cd ..
./buildconf --force
./configure \
    --enable-debug --enable-maintainer-zts \
    --enable-hello=shared
make -j

# Test if it is working
sapi/cli/php \
    -dextension=modules/hello.so \
    -r 'var_dump(extension_loaded("hello"));'

You can now start to enter code to ext/hello/hello.c and create your extension. If you want to compile the changes you make just issue make without arguments.

Since we've compiled using --debug we you can now use gdb to debug the C code and explore how PHP internally works. To start a debugging session use:

gdb sapi/cli/php
...
(gdb) break main
(gdb) run -dextension=modules/hello.so some.php

Of course you'll mostly set breakpoints into your extension functions rather than in the php main() function once you've added code to the extension. However, this should show the basic steps to get there.

Have fun! :)

gdb