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gh-130851: Only intern constants of types generated by the compiler #130901

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Merged
merged 2 commits into from
Mar 7, 2025
Merged

gh-130851: Only intern constants of types generated by the compiler #130901

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5c3dd1c
gh-130851: Only intern constants of types generated by compiler
colesbury Mar 5, 2025
f6670ce
Use _Py_IsImmortal instead of recursive call in should_immortalize_co…
colesbury Mar 7, 2025
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43 changes: 41 additions & 2 deletions Objects/codeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -135,6 +135,44 @@ should_intern_string(PyObject *o)

#ifdef Py_GIL_DISABLED
static PyObject *intern_one_constant(PyObject *op);

// gh-130851: In the free threading build, we intern and immortalize most
// constants, except code objects. However, users can generate code objects
// with arbitrary co_consts. We don't want to immortalize or intern unexpected
// constants or tuples/sets containing unexpected constants.
static int
should_immortalize_constant(PyObject *v)
{
// Only immortalize containers if we've already immortalized all their
// elements.
if (PyTuple_CheckExact(v)) {
for (Py_ssize_t i = PyTuple_GET_SIZE(v); --i >= 0; ) {
if (!_Py_IsImmortal(PyTuple_GET_ITEM(v, i))) {
return 0;
}
}
return 1;
}
else if (PyFrozenSet_CheckExact(v)) {
PyObject *item;
Py_hash_t hash;
Py_ssize_t pos = 0;
while (_PySet_NextEntry(v, &pos, &item, &hash)) {
if (!_Py_IsImmortal(item)) {
return 0;
}
}
return 1;
}
else if (PySlice_Check(v)) {
PySliceObject *slice = (PySliceObject *)v;
return (_Py_IsImmortal(slice->start) &&
_Py_IsImmortal(slice->stop) &&
_Py_IsImmortal(slice->step));
}
return (PyLong_CheckExact(v) || PyFloat_CheckExact(v) ||
PyComplex_Check(v) || PyBytes_CheckExact(v));
}
#endif

static int
Expand Down Expand Up @@ -241,8 +279,9 @@ intern_constants(PyObject *tuple, int *modified)

// Intern non-string constants in the free-threaded build
_PyThreadStateImpl *tstate = (_PyThreadStateImpl *)_PyThreadState_GET();
if (!_Py_IsImmortal(v) && !PyCode_Check(v) &&
!PyUnicode_CheckExact(v) && !tstate->suppress_co_const_immortalization)
if (!_Py_IsImmortal(v) && !PyUnicode_CheckExact(v) &&
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Is the explicit check for unicode necessary, given that should_immortalize_constant also checks that? (For performance, perhaps?)

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The checks were in both places because I wrote should_immortalize_constant recursively for tuples, sets, and slices.

I've changed should_immortalize_constant so that it's no longer recursive and instead interns and immortalizes tuples, set, and slices if we've already immortalized their elements. That should still end up interning and immortalizing the same objects, but avoids the seemingly redundant checks.

should_immortalize_constant(v) &&
!tstate->suppress_co_const_immortalization)
{
PyObject *interned = intern_one_constant(v);
if (interned == NULL) {
Expand Down
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