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gh-128485: ensure that dlmalloc initializes itself at import time in ctypes #131633

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Merged
merged 1 commit into from
Mar 24, 2025
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gh-128485: ensure that dlmalloc initializes itself at import time in ctypes #131633

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18 changes: 12 additions & 6 deletions Modules/_ctypes/_ctypes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -6062,6 +6062,18 @@ _ctypes_add_objects(PyObject *mod)
static int
_ctypes_mod_exec(PyObject *mod)
{
// See https://github.com/python/cpython/issues/128485
// This allocates some memory and then frees it to ensure that the
// the dlmalloc allocator initializes itself to avoid data races
// in free-threading.
void *codeloc = NULL;
void *ptr = Py_ffi_closure_alloc(sizeof(void *), &codeloc);
if (ptr == NULL) {
PyErr_NoMemory();
return -1;
}
Py_ffi_closure_free(ptr);

ctypes_state *st = get_module_state(mod);
st->_unpickle = PyObject_GetAttrString(mod, "_unpickle");
if (st->_unpickle == NULL) {
Expand Down Expand Up @@ -6189,9 +6201,3 @@ PyInit__ctypes(void)
{
return PyModuleDef_Init(&_ctypesmodule);
}

/*
Local Variables:
compile-command: "cd .. && python setup.py -q build -g && python setup.py -q build install --home ~"
End:
*/
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