How to runtime debug shared libraries?

Question

Can anyone tell me how to do runtime debugging on shared libraries?

I need to runtime-debug a function in my shared library, but its called by another program. How c

Answer 1

Another example further to lothar's answer:

I'm running tests on a dynamic library test.so (compiled from test.c) in Linux using python and python's unit-testing library unittest called tests/test_pwmbasic.py. (naming scheme is a bit monotone, I realise that now)

~/my/test/path/
    tests/
        __init__.py
        test_pwmbasic.py
    test.c
    test.so

I want to debug what's in test.so from stimulus in test_pwmbasic.py. So this is how I got it working...

$ cd ~/my/test/path
$ gdb $(which python)
   ... gdb blah ...
(gdb) b test.c:179
(gdb) run
>>> from tests.test_pwmbasic import *
>>> import unittest
>>> unittest.main()
   ... unittest blah ...
Breakpoint 1, pwmTest_setDutyCycles (dutyCycles=0x7ffff7ece910) at ./test.c:179
(gdb) print pwm_errorCode
$1 = PWM_ERROR_NONE

and now I want to marry gdb

note: test.c also includes ../pwm.c, so I can also breakpoint within that library with

(gdb) b pwm.c:123