gh-145559: Add PyUnstable_DumpTraceback() and PyUnstable_DumpTracebackThreads() by alexmalyshev · Pull Request #145560 · python/cpython · GitHub

These functions stopped being exported in #107215. However, they are the only way to print a Python stacktrace safely from a signal handler, making them very useful for extensions. Re-export them.

Issue: Expose signal-safe way to print stacktraces #145559

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Rather than exporting internal C API functions, I would prefer to promote them as public or PyUnstable functions.

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Made them PyUnsafe_ functions. I believe that the mentions to them in the configure and emscripten files can just be deleted now that they'll be public.

I believe they should have PyUnstable_ prefix, not PyUnsafe_.

I believe they should have PyUnstable_ prefix, not PyUnsafe_.

Ack I always make this mistake...

…functions These functions stopped being exported in python#107215. However, they are the only way to print a Python stacktrace safely from a signal handler, making them very useful for extensions. Re-export them as PyUnstable functions.

Please, try to avoid force-push.

…g Limited API

!buildbot emscripten

🤖 New build scheduled with the buildbot fleet by @freakboy3742 for commit 538a1cd 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F145560%2Fmerge

The command will test the builders whose names match following regular expression: emscripten

The builders matched are:

WASM Emscripten PR

Note that PyUnstable_DumpTracebackThreads does not work well on the free-threaded build, because other threads may exit and delete their PyThreadState *. I think it's worth adding a warning for that. Here's an example:

.. warning::
    On the :term:`free-threaded build`, this function is not thread-safe. If
    another thread deletes its :term:`thread state` while this function is being
    called, the process will likely crash.

Comment says 100, but it appears to have been 500 since 2012, 54f939b.

Please also add an entry to the changelog and "What's New in Python 3.15".

For the changelog, you can use blurb_it.
For the "What's New in Python 3.15" page, please add a note under the "C API changes" section (here).

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Something really bad happened here. Can you try to reset the PR? :)

Yeah I screwed something up badly, my bad!

bedevere-app Bot mentioned this pull request Mar 5, 2026

Expose signal-safe way to print stacktraces #145559

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bedevere-app Bot added the awaiting review label Mar 5, 2026

alexmalyshev force-pushed the dump-traceback branch from cb5cf36 to d7f6643 Compare March 5, 2026 18:27

alexmalyshev requested review from AA-Turner, FFY00, ZeroIntensity, corona10, emmatyping, ericsnowcurrently, erlend-aasland and freakboy3742 as code owners March 5, 2026 18:27

alexmalyshev force-pushed the dump-traceback branch from d7f6643 to 28803eb Compare March 5, 2026 19:12

alexmalyshev force-pushed the dump-traceback branch from 28803eb to d0c95ed Compare March 5, 2026 20:39

Add written docs, move decls to cpython/traceback.h to avoid modifyin…

538a1cd

…g Limited API

ZeroIntensity reviewed Mar 6, 2026

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vstinner reviewed Mar 6, 2026

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vstinner changed the title gh-145559: Re-export _Py_DumpTraceback and _Py_DumpTracebackThreads gh-145559: Add PyUnstable_DumpTraceback() and PyUnstable_DumpTracebackThreads() Mar 6, 2026

Move comments into Doc/c-api, fix documented string length

e497d2e

Comment says 100, but it appears to have been 500 since 2012, 54f939b.

ZeroIntensity reviewed Mar 6, 2026

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Comment thread Doc/c-api/exceptions.rst Outdated

Comment thread Doc/c-api/exceptions.rst Outdated

Comment thread Doc/c-api/exceptions.rst Outdated

Address comments on C API docs, add whatsnew entry

50e6501

alexmalyshev requested review from a team, DinoV, Fidget-Spinner, Yhg1s, brandtbucher, brettcannon, diegorusso, ezio-melotti, iritkatriel, methane, mhsmith, ncoghlan, sethmlarson, tomasr8 and webknjaz as code owners April 5, 2026 20:55

StanFromIreland closed this Apr 5, 2026

StanFromIreland removed request for a team, ambv, berkerpeksag, brettcannon, freakboy3742, gpshead, mhsmith and vsajip April 5, 2026 21:11

alexmalyshev mentioned this pull request Apr 5, 2026

gh-145559: Add PyUnstable_DumpTraceback() and PyUnstable_DumpTracebackThreads() #148145

Merged

vstinner mentioned this pull request Jul 19, 2026

gh-145559: Make PyUnstable_DumpTraceback return void again #154131

Closed

gh-145559: Add PyUnstable_DumpTraceback() and PyUnstable_DumpTracebackThreads() by alexmalyshev · Pull Request #145560 · python/cpython · GitHub

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gh-145559: Add PyUnstable_DumpTraceback() and PyUnstable_DumpTracebackThreads()#145560alexmalyshev wants to merge 220 commits intopython:mainpython/cpython:mainfrom alexmalyshev:dump-tracebackalexmalyshev/cpython:dump-tracebackCopy head branch name to clipboard

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gh-145559: Add PyUnstable_DumpTraceback() and PyUnstable_DumpTracebackThreads()#145560
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