gh-140729: profiling or tracing multiprocessing can cause error

[yihong0618]

This patch fix can not cporfile or profile with multiprocessing

add Co-author @YvesDup with credit.

# cat ttt.py
import concurrent.futures


def worker(x):
    return x * 2


if __name__ == "__main__":
    with concurrent.futures.ProcessPoolExecutor() as executor:
        results = list(executor.map(worker, [1, 2, 3]))
        print(f"Results: {results}")

./python.exe -m profile ttt.py 
./python.exe -m cProfile ttt.py 

and this patch is also expert @gaogaotiantian 's fix idea more can check: #116141

• Issue: 3.15 profiling, can't use ProcessPoolExecutor.map() in a simple script #140729

[YvesDup]

@yihong0618 thank you for creating this PR. I was waiting for figure out why or how setting the __spec__ field to None fixed this. And for now, I desperately have no answer.

[YvesDup]

./python.exe -m profile ttt.py

About the profile module, see #140729 (comment). Only the cProfile module should be fix.

[yihong0618]

./python.exe -m profile ttt.py

About the profile module, see #140729 (comment). Only the cProfile module should be fix.

copy that will fix it

[YvesDup]

By removing spec value to the __spec__key, does the comment above still apppropriate ?
Should not we replace it here with a reference to the issue and @gaogaotiantian original fix ?

[gaogaotiantian]

So my original "source" is https://docs.python.org/3/reference/import.html#module-specs - where it says the __main__ module normally sets __spec__ to None. But it's for my individual project so as long as it works it's fine. Not sure about the very accurate and official answer.

[yihong0618]

By removing spec value to the __spec__key, does the comment above still apppropriate ? Should not we replace it here with a reference to the issue and @gaogaotiantian original fix ?

remove is not right still fail...we the right is set it to None

[YvesDup]

remove is not right still fail...we the right is set it to None

You are right.

How about adding a comment such as:
See gh-140729: set None to __spec__ according to the documentation (https://docs.python.org/3/reference/import.html#module-specs)

[yihong0618]

the original fixed from gaotian do not add it, I follow it style~

[yihong0618]

./python.exe -m profile ttt.py

About the profile module, see #140729 (comment). Only the cProfile module should be fix.

fixed