make gdb load a shared library from a specific path

Question

I got a core while executing an application and I saved the executable, the corefile and a shared library which the application use in /tmp to check them later. I then modified the library, rebuilt it and started the executable again. Now when I am trying to debug the core, gdb is loading the shared library from its original path and not from the directory /tmp where I saved the original library.

For example, the original path was /opt/mydir/lib/libmylib.so.0. gdb is loading this shared library, while I want it to load /tmp/libmylib.so.0. The application also uses some standard libraries which are in /usr/lib and /lib directories so I don't want these paths to get changed. Just want to change /opt/mydir/lib/ -> /tmp. How can I do that?

Answer 1

The simplest solution is to temporarily restore /opt/mydir/lib/libmylib.so.0 to the copy that was used at crash time (i.e. the one now in /tmp), analyse the core, then restore back the new version.

If you don't want to do that, set solib-search-path and set sysroot are your friends.

Note that you must set both before loading the core. This sequence should work:

(gdb) set sysroot /no/such/file
(gdb) set solib-search-path /tmp:/usr/lib:/lib
(gdb) core /tmp/core