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gh-152503: Fix garbage text from curses wide-character cell reads #152505

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Merged
serhiy-storchaka merged 1 commit into from
Jun 29, 2026
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gh-152503: Fix garbage text from curses wide-character cell reads #152505

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4 changes: 4 additions & 0 deletions Misc/NEWS.d/next/Library/2026-06-28-16-20-07.gh-issue-152503.N55ose.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
Fix :meth:`curses.window.in_wch`, :meth:`curses.window.in_wchstr` and
:meth:`curses.window.getbkgrnd` returning garbage text when :mod:`curses` is
built against a curses library that does not NUL-terminate the ``cchar_t``
text array (such as NetBSD curses).
14 changes: 11 additions & 3 deletions Modules/_cursesmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -765,6 +765,9 @@ static int
curses_getcchar(const cchar_t *wcval, wchar_t *wstr, attr_t *attrs, int *pair)
{
short spair = 0;
/* getcchar() is not guaranteed to write the text of an empty cell, so make
the output an empty string by default. */
wstr[0] = L'\0';
#if _NCURSES_EXTENDED_COLOR_FUNCS
int rtn = getcchar(wcval, wstr, attrs, &spair, pair);
#else
Expand Down Expand Up @@ -3049,7 +3052,8 @@ _curses_window_in_wch_impl(PyCursesWindowObject *self, int group_right_1,
int y, int x)
/*[clinic end generated code: output=846ca8a82f2ecab4 input=a55dd215367dfbb1]*/
{
curses_cell_t wcval;
/* Zeroed so getcchar() sees a NUL-terminated text array on read. */
curses_cell_t wcval = {0};
cursesmodule_state *state = get_cursesmodule_state_by_win(self);
#ifdef HAVE_NCURSESW
int rtn;
Expand Down Expand Up @@ -3096,7 +3100,8 @@ static PyObject *
_curses_window_getbkgrnd_impl(PyCursesWindowObject *self)
/*[clinic end generated code: output=afec19cad00eff71 input=e06bf3d6bf90d2ec]*/
{
curses_cell_t wcval;
/* Zeroed so getcchar() sees a NUL-terminated text array on read. */
curses_cell_t wcval = {0};
cursesmodule_state *state = get_cursesmodule_state_by_win(self);
#ifdef HAVE_NCURSESW
if (wgetbkgrnd(self->win, &wcval) == ERR) {
Expand Down Expand Up @@ -3812,7 +3817,10 @@ PyCursesWindow_in_wchstr(PyObject *op, PyObject *args)

n = Py_MIN(n, max_buf_size - 1);
cursesmodule_state *state = get_cursesmodule_state_by_win(self);
curses_cell_t *buf = PyMem_New(curses_cell_t, n + 1);
/* Zero the cells: reading a cell back through getcchar() relies on the
cchar_t text array being NUL-terminated, which some curses libraries
only guarantee for the characters they actually write. */
curses_cell_t *buf = PyMem_Calloc(n + 1, sizeof(curses_cell_t));
if (buf == NULL) {
return PyErr_NoMemory();
}
Expand Down
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