Does xulrunner depend on GNOME or not?

Question

Hi... I have two questions (the rest is just me talking about how confused I am):
1. How is mozilla getting its files to use shared libraries even when they aren't linked against those shared libraries?
2. How can I tell if it's safe to delete a shared library that is used in only this way?
=====
I know xulrunner comes with two files in /usr/lib/xulrunner-1.9.2/components that bring in gnome dependencies: libmozgnome.so and libnkgnomevfs.so. Firefox also comes with libnkgnomevfs.so but according to this bug https://bugzilla.mozilla.org/show_bug.cgi?id=512671 it's not supposed to.
I'm wondering how these libraries actually get used.
[root@connors-laptop firefox-3.6]# cd /usr/lib/firefox-3.6
[root@connors-laptop firefox-3.6]# ldd firefox | grep gnome
[root@connors-laptop firefox-3.6]# cd /usr/lib/xulrunner-1.9.2/
[root@connors-laptop xulrunner-1.9.2]# ldd libxul.so | grep gnome
[root@connors-laptop xulrunner-1.9.2]# ldd libxpcom.so | grep gnome
[root@connors-laptop xulrunner-1.9.2]# ldd libmozjs.so | grep gnome
[root@connors-laptop xulrunner-1.9.2]#
As far as I can tell... NOTHING is linked against them. However the situation gets even weirder. I know that libxul and libxpcom are essential for firefox, yet firefox seems not to be linked against them either:
[root@connors-laptop firefox-3.6]# ldd firefox | grep libxul
[root@connors-laptop firefox-3.6]# ldd firefox | grep libxpcom
[root@connors-laptop firefox-3.6]# grep libxul firefox
Binary file firefox matches
[root@connors-laptop firefox-3.6]# grep libxpcom firefox
Binary file firefox matches
[root@connors-laptop firefox-3.6]#
The binary seems to contain references to them but they are runtime references, not compile time references? It dynamically decides whether or not it should use those libraries when you start it? I tried figuring out where the gnome libraries are used this way and I think I found it:
[root@connors-laptop firefox-3.6]# cd /usr/lib/xulrunner-1.9.2/
[root@connors-laptop xulrunner-1.9.2]# grep gnome libxul.so
Binary file libxul.so matches
Thunderbird is causing similar confusion with me. It is of course independent from xulrunner but it comes with a libmozgnome.so and I can't tell how it's used. Anecdotally everyone says it's safe to delete libmozgnome and libnkgnomevfs but how do I know this? If I deleted orphan libraries that things aren't linked against I would delete libxul, libxpcom and libmozjs which is obviously NOT okay to do.

Answer 1

Ok so when I start the code... it is "deciding" whether to be linked against libmozgnome.so or not. Sounds a bit like self-modifying code to me. I was wondering because if I made a program that used gconf for example, even if I wanted it to be "optional" and put it in a section of the program that I considered "unimportant"... if I didn't have gconf installed I would absolutely get an undefined reference to symbol and nothing would work... even if I think it's "not a big deal."
I guess this LD_PRELOAD stuff is the solution. Firefox can first check if the right gnome deps are installed. If they are, it will load them at run time, if they are missing it will just move on. I guess this is how openoffice uses the "optional" gconf. It comes with a file called gconfbe1.uno.so but nothing is linked (at compile time) to it. This must mean it is loaded while openoffice runs because openoffice detected at runtime that I have gconf but if I didn't it would've skipped this dependency.
So ldd is not a good way to check if a program does this. I should use lsof to see if a program is dynamically loading libraries? And if I want to confirm my suspicions about how it does so I should grep the executable for phrases like "LD_PRELOAD", "LD_LIBRARY_PATH" or "dlopen"? I guess the ultimate way would be checking the source code if I have time.