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gh-120608: Make reversed iterator work with free-threading (#120971)

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Co-authored-by: Sam Gross <colesbury@gmail.com>
Co-authored-by: Kumar Aditya <kumaraditya@python.org>
Co-authored-by: Łukasz Langa <lukasz@langa.pl>
This commit is contained in:
Pieter Eendebak 2025-03-12 12:39:52 +01:00 • committed by GitHub
parent 4dcbe06fd2
commit 1fb7e2aeb7
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GPG key ID: B5690EEEBB952194
4 changed files with 65 additions and 10 deletions
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29
Objects/enumobject.c
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@ -439,20 +439,22 @@ reversed_next(PyObject *op)
{
reversedobject *ro = _reversedobject_CAST(op);
PyObject *item;
Py_ssize_t index = ro->index;
Py_ssize_t index = FT_ATOMIC_LOAD_SSIZE_RELAXED(ro->index);
if (index >= 0) {
item = PySequence_GetItem(ro->seq, index);
if (item != NULL) {
ro->index--;
FT_ATOMIC_STORE_SSIZE_RELAXED(ro->index, index - 1);
return item;
}
if (PyErr_ExceptionMatches(PyExc_IndexError) ||
PyErr_ExceptionMatches(PyExc_StopIteration))
PyErr_Clear();
}
ro->index = -1;
FT_ATOMIC_STORE_SSIZE_RELAXED(ro->index, -1);
#ifndef Py_GIL_DISABLED
Py_CLEAR(ro->seq);
#endif
return NULL;
}
@ -461,13 +463,15 @@ reversed_len(PyObject *op, PyObject *Py_UNUSED(ignored))
{
reversedobject *ro = _reversedobject_CAST(op);
Py_ssize_t position, seqsize;
Py_ssize_t index = FT_ATOMIC_LOAD_SSIZE_RELAXED(ro->index);
if (ro->seq == NULL)
if (index == -1)
return PyLong_FromLong(0);
assert(ro->seq != NULL);
seqsize = PySequence_Size(ro->seq);
if (seqsize == -1)
return NULL;
position = ro->index + 1;
position = index + 1;
return PyLong_FromSsize_t((seqsize < position) ? 0 : position);
}
@ -477,10 +481,13 @@ static PyObject *
reversed_reduce(PyObject *op, PyObject *Py_UNUSED(ignored))
{
reversedobject *ro = _reversedobject_CAST(op);
if (ro->seq)
Py_ssize_t index = FT_ATOMIC_LOAD_SSIZE_RELAXED(ro->index);
if (index != -1) {
return Py_BuildValue("O(O)n", Py_TYPE(ro), ro->seq, ro->index);
else
}
else {
return Py_BuildValue("O(())", Py_TYPE(ro));
}
}
static PyObject *
@ -490,7 +497,11 @@ reversed_setstate(PyObject *op, PyObject *state)
Py_ssize_t index = PyLong_AsSsize_t(state);
if (index == -1 && PyErr_Occurred())
return NULL;
if (ro->seq != 0) {
Py_ssize_t ro_index = FT_ATOMIC_LOAD_SSIZE_RELAXED(ro->index);
// if the iterator is exhausted we do not set the state
// this is for backwards compatibility reasons. in practice this situation
// will not occur, see gh-120971
if (ro_index != -1) {
Py_ssize_t n = PySequence_Size(ro->seq);
if (n < 0)
return NULL;
@ -498,7 +509,7 @@ reversed_setstate(PyObject *op, PyObject *state)
index = -1;
else if (index > n-1)
index = n-1;
ro->index = index;
FT_ATOMIC_STORE_SSIZE_RELAXED(ro->index, index);
}
Py_RETURN_NONE;
}