Bug report

Bug description:

Original gist: https://gist.github.com/devdanzin/ed7691a99c26ede561a549ab1dba00b2

Summary

In Modules/_lsprof.c (lines 821-823), when sys.monitoring.use_tool_id() fails, PyErr_Format unconditionally replaces the real exception with a generic ValueError.

Fix

Remove the PyErr_Format call and let the original exception propagate.

Reproducer

import cProfile
p1 = cProfile.Profile()
p1.enable()
p2 = cProfile.Profile()
try:
    p2.enable()  # ValueError: "Another profiling tool is already active"
except ValueError as e:
    print(f"Generic message masks real error: {e}")
finally:
    p1.disable()

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-153068: Preserve cprofile enable errors #153070
• [3.13] gh-153068: Preserve cprofile enable errors (GH-153070) #153240
• [3.15] gh-153068: Preserve cprofile enable errors (GH-153070) #153241
• [3.14] gh-153068: Preserve cprofile enable errors (GH-153070) #153242