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gh-141563: make PyDateTime_IMPORT thread-safe #144210

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gh-141563: make PyDateTime_IMPORT thread-safe #144210

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c3f4649
make PyDateTime_IMPORT thread-safe
kumaraditya303 Jan 24, 2026
36a06c8
use static inline function
kumaraditya303 Jan 24, 2026
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17 changes: 15 additions & 2 deletions Include/datetime.h
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Original file line number Diff line number Diff line change
Expand Up @@ -196,8 +196,21 @@ typedef struct {
/* Define global variable for the C API and a macro for setting it. */
static PyDateTime_CAPI *PyDateTimeAPI = NULL;

#define PyDateTime_IMPORT \
PyDateTimeAPI = (PyDateTime_CAPI *)PyCapsule_Import(PyDateTime_CAPSULE_NAME, 0)
static inline PyDateTime_CAPI *
PyDateTime_IMPORT(void) {
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@vstinner vstinner Jan 27, 2026

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The intended usage is just PyDateTime_IMPORT;. We need more black magic here:

  • Rename PyDateTime_IMPORT() to _PyDateTime_IMPORT()
  • Add #define PyDateTime_IMPORT _PyDateTime_IMPORT() macro

PyDateTime_CAPI *val = _Py_atomic_load_ptr(&PyDateTimeAPI);
if (val == NULL) {
PyDateTime_CAPI *capi = (PyDateTime_CAPI *)PyCapsule_Import(
PyDateTime_CAPSULE_NAME, 0);
if (capi != NULL) {
/* if the compare exchange fails then in that case
another thread would have initialized it */
_Py_atomic_compare_exchange_ptr(&PyDateTimeAPI, &val, (void *)capi);
return capi;
}
}
return val;
}

/* Macro for access to the UTC singleton */
#define PyDateTime_TimeZone_UTC PyDateTimeAPI->TimeZone_UTC
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