Issue #25155: Add _PyTime_AsTimevalTime_t() function

On Windows, the tv_sec field of the timeval structure has the type C long,
whereas it has the type C time_t on all other platforms. A C long has a size of
32 bits (signed inter, 1 bit for the sign, 31 bits for the value) which is not
enough to store an Epoch timestamp after the year 2038.

Add the _PyTime_AsTimevalTime_t() function written for datetime.datetime.now():
convert a _PyTime_t timestamp to a (secs, us) tuple where secs type is time_t.
It allows to support dates after the year 2038 on Windows.

Enhance also _PyTime_AsTimeval_impl() to detect overflow on the number of
seconds when rounding the number of microseconds.

1 files changed, 5 insertions, 4 deletions

diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index 7e4be5b..662dcbc 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -4113,13 +4113,14 @@ static PyObject *
 datetime_best_possible(PyObject *cls, TM_FUNC f, PyObject *tzinfo)
 {
     _PyTime_t ts = _PyTime_GetSystemClock();
-    struct timeval tv;
+    time_t secs;
+    int us;
 
-    if (_PyTime_AsTimeval(ts, &tv, _PyTime_ROUND_FLOOR) < 0)
+    if (_PyTime_AsTimevalTime_t(ts, &secs, &us, _PyTime_ROUND_FLOOR) < 0)
         return NULL;
-    assert(0 <= tv.tv_usec && tv.tv_usec <= 999999);
+    assert(0 <= us && us <= 999999);
 
-    return datetime_from_timet_and_us(cls, f, tv.tv_sec, tv.tv_usec, tzinfo);
+    return datetime_from_timet_and_us(cls, f, secs, us, tzinfo);
 }
 
 /*[clinic input]