Unless I missed it, looking at https://github.com/python/cpython/blob/main/Lib/pdb.py, https://github.com/python/cpython/blob/main/Lib/inspect.py, and https://docs.python.org/3/library/pdb.html doesn't give much of a clue how to provide sources to exec-generated code.

I may have misread, but pdb *seems* to lean on inspect.findsource which eventually excludes sources that match `^<.*>$` (like `<string>`).

Running attached test_case.py:

% python test_case.py
> <string>(4)foo()
(Pdb) l
[EOF]
(Pdb) c
inspect.getfile(<function foo at 0x10b735160>): <string>
calling inspect.findsource(<function foo at 0x10b735160>) ...
Traceback (most recent call last):
  File "/Users/matt/Documents/dev/numerary/test_case.py", line 12, in <module>
    foo()
  File "/Library/Frameworks/MacPorts-20200907/Python.framework/Versions/3.9/lib/python3.9/inspect.py", line 835, in findsource
    raise OSError('could not get source code')
OSError: could not get source code