Description

methane

opened on May 7, 2024

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Feature or enhancement

Proposal:

CPython hides PyFrameObject internals so Cython include pycore_frame.h to set f_lineno.
Let's provide PyFrame_SetLineNumber() for Cython.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

#117551 (comment)

Linked PRs

• gh-118720: Add PyFrame_SetLineNumber() function #131246

Activity

1. methane

   added

   type-featureA feature request or enhancementA feature request or enhancement

   topic-C-API

   on May 7, 2024
2. Ben4C commented on Aug 14, 2024

   

   Ben4C

   on Aug 14, 2024

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   Hello, I've been working on this for a little while, but I'm a bit lost on implementing the changes.

   From what I understand think I'm supposed to create a public API to set the f_fileno variable so I used PyAPI_FUNC(int) PyFrame_SetLineNumber(PyFrameObject *f, int lineno) in Include/cpython/frameobject.h which uses frame_setlineno from frameobject.c to change the f_lineno. I've been trying to get a test to pass to verify that this works in
   Lib/test/test_frame.py but I'm not sure if my approach or logic is correct.

   This is what I have so far: Ben4C@1e82093

   Reacted by Inada Naoki
3. vstinner

   added 3 commits that reference this issue on Mar 14, 2025

   pythongh-118720: Add PyFrame_SetLineNumber() function

   9a8d371

   pythongh-118720: Add PyFrame_SetLineNumber() function

   09cbced

   pythongh-118720: Add PyFrame_SetLineNumber() function

   dcf27bf
4. vstinner commented on Mar 14, 2025

   

   vstinner

   on Mar 14, 2025

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   This function was also discussed at #130931.
5. vstinner commented on Mar 14, 2025

   

   vstinner

   on Mar 14, 2025

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   I wrote PR gh-131246 to add PyFrame_SetLineNumber().
6. picnixz

   added

   interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)

   on Mar 14, 2025
7. markshannon commented on Mar 17, 2025

   

   markshannon

   on Mar 17, 2025

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   I think is going to be very confusing if PyFrame_SetLineNumber has different behavior from setting the line number in Python frame.f_lineno = ....

   The f_lineno field in the the frame object is a cache for the computed line number.
   It may overwritten by the interpreter, so setting it will not work reliably.
8. vstinner commented on Mar 17, 2025

   

   vstinner

   on Mar 17, 2025

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   I wrote this function to replace the Cython macro:

   #define __Pyx_PyFrame_SetLineNumber(frame, lineno) (frame)->f_lineno = (lineno)

   I suppose that Cython sets f_lineno to produce a traceback with specific line number.

   cc @scoder @da-woods
9. da-woods commented on Mar 17, 2025

   

   da-woods

   on Mar 17, 2025

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   I suppose that Cython sets f_lineno to produce a traceback with specific line number.

   Yes - it's used directly after creating a frame for that purpose.

   (It's also used in the old, pre-sys-monitoring code. I would not worry about replacing that usage because I think that's only on older Python versions)
10. markshannon commented on Mar 18, 2025

    

    markshannon

    on Mar 18, 2025

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    So what are the proposed semantics of PyFrame_SetLineNumber(), how do we test it?

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