gh-148932: Fix profiling.sampling on Windows virtual environments

[edvilme]

Currently, it is not possible to run profiling.sampling from a Windows venv because virtual environments use shims to launch the original interpreter, but the shim itself isn't a real Python process.

Fix

Added _resolve_venv_child function to detect when the profiler is started from a virtual environment process on Windows, and automatically redirect it to the real child Python process. This prevents profiling against the shim instead of the actual Python process.

The SampleProfiler class uses the resolved child PID when initializing.

Before

(venv) PS C:\Users\user\Documents\project> python -m profiling.sampling run .\test.py
Running profiling.sampling from virtualenv on Windows platform is not supported

After

(venv) PS C:\Users\user\Documents\project> python -m profiling.sampling run .\test.py
Profile Stats:
       nsamples   sample%  tottime (ms)    cumul%  cumtime (ms)  filename:lineno(function)
        465/465      24.6       465.000      24.6       465.000  test.py:59(bubble_sort)
        452/589      24.0       452.000      31.2       589.000  test.py:27(fibonacci_recursive)
        400/400      21.2       400.000      21.2       400.000  test.py:60(bubble_sort)
        227/227      12.0       227.000      12.0       227.000  test.py:72(matrix_multiply)
        130/130       6.9       130.000       6.9       130.000  test.py:58(bubble_sort)
         95/123       5.0        95.000       6.5       123.000  test.py:25(fibonacci_recursive)
          27/27       1.4        27.000       1.4        27.000  test.py:71(matrix_multiply)
          23/23       1.2        23.000       1.2        23.000  test.py:26(fibonacci_recursive)
          19/31       1.0        19.000       1.6        31.000  test.py:23(fibonacci_recursive)
            9/9       0.5         9.000       0.5         9.000  test.py:34(is_prime)
            7/7       0.4         7.000       0.4         7.000  test.py:35(is_prime)
            6/6       0.3         6.000       0.3         6.000  test.py:84(compute_collatz)
            4/8       0.2         4.000       0.4         8.000  random.py:342(Random.randint)
            3/3       0.2         3.000       0.2         3.000  random.py:339(Random.randint)
            3/3       0.2         3.000       0.2         3.000  test.py:80(compute_collatz)

Legend:
  nsamples: Direct/Cumulative samples (direct executing / on call stack)
  sample%: Percentage of total samples this function was directly executing
  tottime: Estimated total time spent directly in this function
  cumul%: Percentage of total samples when this function was on the call stack
  cumtime: Estimated cumulative time (including time in called functions)
  filename:lineno(function): Function location and name

• Issue: profiling.sampling doesn't work under venv on Windows #148932

CC @pablogsal

[read-the-docs-community]

Documentation build overview

📚 cpython-previews | 🛠️ Build #32999827 | 📁 Comparing deb4711 against main (9242700)

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98 files changed · + 1 added · ± 97 modified

+ Added

• howto/abi3t-migration.html

± Modified

• bugs.html
• glossary.html
• c-api/complex.html
• c-api/exceptions.html
• c-api/interp-lifecycle.html
• c-api/perfmaps.html
• c-api/stable.html
• c-api/structures.html
• c-api/threads.html
• c-api/typehints.html
• and 87 more...

[chris-eibl]

I've just verified locally that it works in a virtual environment now, so approving.

Thanks for your contribution @edvilme!

I'd even backport to 3.15 (rather a bug fix than a feature IMO), but leave the final decision to @pablogsal.

[edvilme]

Hi @chris-eibl thank you!!
I agree it is a bug fix, should I do anything for the backport?

[chris-eibl]

No, thanks. Let's wait for Pablo's decision first, and then most probably bedevere-bot can take care of it, anyway.

[pablogsal]

LGTM! Great work @edvilme

[pablogsal]

Please address that nit and ping me again so I or @chris-eibl can land

[edvilme]

Renamed method to _resolve_python_pid
CC @pablogsal