GeezerVison is showing github.com — Exact reporting of `curses` C function failures · Issue #133579 · python/cpython
Exact reporting of curses C function failures #133579DescriptionWhen calling some curses C functions, we ignore their return values. Those are:
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in PyCursesWindow_dealloc, we ignore delwin() errors
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in _curses_initscr_impl, we ignore wrefresh() errors
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in _curses_window_addstr_impl, we ignore wattrset() errors and prefer reporting errors due to adding strings. Same for the insstr* functions
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in _curses_window_box_impl, we ignore the error returned by box(). This is correct because the manual says (for box):
All routines return the integer OK. The SVr4.0 manual says "or a non-negative integer if immedok is set", but this appears to be an error. X/Open does not define any error conditions. This implementation returns an error if the window pointer is null.
In this case, I think it's better to explicitly suppress the return value and link the manpage.
The question now is:
- What should we do for a failing
delwin() in the destructor?
- What should we do for
wattrset() when this routine is not the "important" one?
cc @encukou
Note We will not backport these fixes as they could break existing code that could be surprised by a new exception.
Linked PRs
Activityencukou commented on May 17, 2025
What should we do for a failing delwin() in the destructor?
Set an exception and call PyErr_WriteUnraisable, so that it's caught by unraisablehook.
What should we do for wattrset() when this routine is not the "important" one?
In _curses_window_addstr_impl, wattrset is only called if the user explicitly called addstr with an attr argument. Failure to set them should be a hard error, to be handled by the user.
_curses_window_box_impl
IMO, if an error is reported, something is wrong and we should raise an exception.
IMO, these would be bugfixes, but should not be backported. picnixz commented on May 18, 2025 Thanks. I've found other occurrences where curses C functions are called but the error handling is not done. It's just that it was sometimes under ifdef that I missed. I need #125844 to be merged first so that I can use the helpers out there so I'm holding this work for now. picnixz commented on May 19, 2025 On failure, _curses.window.getstr also return an empty string instead of reporting the error. It may be fine, but I don't know if it wouldn't be better to actually report the possible error.
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