PHP extension library dependency - php

Question

I have an extenal dependency for my PHP extension which I am struggling to compile successfully. I would like this extension to be a standalone shared object, which as I understand it is the job of phpize. How do I go about compiling this shared PHP extension with an object file c.o?
The manual compile for a standalone application would look as follows:
gcc -Wall -o php_library main.c c.o
and for a shared library:
gcc -Wall -shared -fPIC -o php_library.so main.c c.o
I understand that there are macros for adding in shared library dependencies by modifying config.m4 such as: PHP_ADD_LIBRARY(pthread,,EXTENSION_SHARED_LIBADD), but I'm not sure how to go about adding in my dependency at compile time. Is there a macro similar to the above for this use case?
It is worth noting that I do not have access to the depdency code, so c.o cannot be modified to solve this problem.

Answer 1

From what I understand from your question, you have an object file c.o which was not compiled to have position-independent code (i.e. -fPIC option) that you want to link into your PHP extension. In this case you must static link it alongside the extension code and any shared libraries. There are a couple ways to do this in the config.m4 file.
The first is to set CFLAGS to pass the name of the object code file to the linker like so:
CFLAGS=-Wl,c.o
The second is to modify LDFLAGS:
LDFLAGS=c.o
When I try the second one I get the following warning during compilation:
*** Warning: Linking the shared library testbed.la against the non-libtool
*** objects c.o is not portable!
Everything works either way so I'm not sure what's up with the warning. But the first method doesn't generate the warning.
Here's a complete sample config.m4:
PHP_ARG_ENABLE(testbed, whether to enable testbed support,
[ --enable-testbed Enable testbed support])
if test "$PHP_TESTBED" = "yes"; then
AC_DEFINE(HAVE_TESTBED, 1, [Whether you have testbed support])
PHP_NEW_EXTENSION(testbed, testbed.c, $ext_shared)
#LDFLAGS=c.o
CFLAGS=-Wl,c.o
fi
I hope this answers the question.