How to link to shared lib from shared lib with relative path?

22
votes

I'm working on a Firefox plugin that uses external libraries to render 3D graphics on the browser.

The problem is that I want the plugin to use external libraries packed with it without changing the LD_LIBRARY_PATH variable.
The libraries are installed in a position relative to the plugin (a shared library too), while the actual executable (i.e. the browser) can be located somewhere entirely else.

I'm testing it on Ubuntu (no problem at Windows version of the plugin) My dependencies are OpenSceneGraph libraries and static compilation will make the plugin really big (not an option if there is another one).

3
linuxgcclinkershared-libraries
This could be useful: stackoverflow.com/questions/3015411/… – Dmitry Yudakov
Interesting, i can confirm that with a simple test program. It uses dlopen() to load a lib1 and lib1 links to a lib2 and uses $ORIGIN to load it from a relative path. This works without problems. – Georg Fritzsche

3 Answers

28
votes

Use the rpath option when linking and specify the 'special' path $ORIGIN.

Example:

-Wl,-R,'$ORIGIN/../lib'

Here's a site that elaborates on using $ORIGIN: http://www.itee.uq.edu.au/~daniel/using_origin/

0
votes

You could maybe use the -L flag during the compilation to specify the relative path where the linker can find your shared objects.

If you have already generated your lib, you can link by directly invoking the ldcommand.

Tips : You can easily check if some symbols are defined in a lib using the unix command nm. This is a useful way to check that the linking is well-done.

(If I were you, I would just change temporaly the LD_LIBRARY_PATH as you said in your post. Why don't you want to do this ?)

-2
votes

It's wrong to use relative rpath for security reason,

You should use libdl functions (dlopen, etc)