Debug cpp Modules Imported by Python

Problem

I found a bug when building my model with mxnet, see here. It seems mxnet people are busy doing other things, therefore I have to solve this by myself. When I am trying to debug mxnet package using lldb with the following command:

lldb -- python test.py

and the following command to set a breakpoint in file:

b file:line

lldb cannot successfully set the breakpoint. It seems the python module is not loaded at that time and lldb cannot find the breakpoint.

Solution

If the problem is on the module loading, we can set a breakpoint in python using

pdb.set_trace()

and open another term, attach lldb to the python process using

attach --pid XXXX
continue

then set the breakpoint, using the absolute path

b \Users\odin\local\mxnet\src\imperative\imperative.cc:300

and continue in pdb.

The breakpoint is then successfully set.