Nested profiling with cProfile raises exception in Python 3.12.

[manueljacob]

Bug report

Bug description:

import cProfile

p1 = cProfile.Profile()
p1.enable()

p2 = cProfile.Profile()
p2.enable()

In Python 3.11 this used to pass, but in Python 3.12 the last line raises “ValueError: Another profiling tool is already active”.

CPython versions tested on:

3.12

Operating systems tested on:

Linux

[gaogaotiantian]

This is a delibrate change, well you can call it a breaking change, but it's not a bug.

Nested profiler never (really) works in Python, the code you give is more like a "don't do this" example. It is equivalent (in Python 3.11) to

import cProfile

p1 = cProfile.Profile()
p1.enable()

p2 = cProfile.Profile()
# p1 is silently disabled here
p1.disable()
p2.enable()

That's not nested, that's just sequential profiling with two profilers - and if you really want to do that, you should be explicit!

A nested profiler should either

• Be able to log what happens in the inner profiler from the outer profiler(which it can't)
• Or at least for the outer profiler to continue to work after the inner profiler finishes(which it can't either)

Yes, the code given won't "report an error" in Python 3.11, but it also won't behave expectedly, it just keeps its mouth shut. I'd consider an error for "this is not how it's going to work!" as an improvement :)