If an error happens in the callback or in converting result of the callback, it is handled by calling PyErr_FormatUnraisable(). If an error happens in preparing arguments for the callback, it is handled in different way -- some message is printed to stderr and then PyErr_Print() is called. In one case the error is not properly handled.

It is better to handle all errors in the uniform way. PyErr_Print() is not suitable for it because it treats SystemExit specially and has a side effect of setting sys.last_exc` and other variables.

Linked PRs

• gh-129502: Fix handling errors in ctypes callbacks #129504
• [3.13] gh-129502: Fix handling errors in ctypes callbacks (GH-129504) #129517
• [3.12] gh-129502: Fix handling errors in ctypes callbacks (GH-129504) #129639