Add C API to notify when tracing/profiling is enabled or disabled

[SubbaraoGarlapati]

Feature or enhancement

Proposal:

There is currently no way to be notified when tracing/profiling is enabled or disabled. This forces tools that want different behavior based on tracing/profiling enablement (e.g., JIT compilers) to poll on every function call, adding significant overhead.
PEP-523 established frame evaluation hooks as an officially supported extension point for JITs. However, JITs using this API have no efficient way to know when tracing/profiling is enabled and fall back to the interpreter.
I propose adding a small C API enhancement allowing callbacks to be registered when trace/profile functions are set or cleared.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-144690: Add C API for trace/profile callback registration #144691

[ZeroIntensity]

I think this would benefit from a discussion on DPO; the motivation is not entirely clear to me, and it seems you could achieve the detection you want by installing an audit hook for sys.settrace. Could you provide some concrete examples of how this would be useful in practice?

[SubbaraoGarlapati]

@ZeroIntensity thanks for the review and feedback - opened a discussion here.