Issue #11576: Fixed timedelta subtraction glitch on big timedelta values
diff --git a/Lib/datetime.py b/Lib/datetime.py
index 47e54ec..1ae7cb5 100644
--- a/Lib/datetime.py
+++ b/Lib/datetime.py
@@ -485,7 +485,11 @@
def __sub__(self, other):
if isinstance(other, timedelta):
- return self + -other
+ # for CPython compatibility, we cannot use
+ # our __class__ here, but need a real timedelta
+ return timedelta(self._days - other._days,
+ self._seconds - other._seconds,
+ self._microseconds - other._microseconds)
return NotImplemented
def __rsub__(self, other):
diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index e9ceee6..38f3b8f 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -383,6 +383,12 @@
for i in range(-10, 10):
eq((i*us/-3)//us, round(i/-3))
+ # Issue #11576
+ eq(td(999999999, 86399, 999999) - td(999999999, 86399, 999998),
+ td(0, 0, 1))
+ eq(td(999999999, 1, 1) - td(999999999, 1, 0),
+ td(0, 0, 1))
+
def test_disallowed_computations(self):
a = timedelta(42)
diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index 6195940..6ee5317 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -1801,13 +1801,14 @@
if (PyDelta_Check(left) && PyDelta_Check(right)) {
/* delta - delta */
- PyObject *minus_right = PyNumber_Negative(right);
- if (minus_right) {
- result = delta_add(left, minus_right);
- Py_DECREF(minus_right);
- }
- else
- result = NULL;
+ /* The C-level additions can't overflow because of the
+ * invariant bounds.
+ */
+ int days = GET_TD_DAYS(left) - GET_TD_DAYS(right);
+ int seconds = GET_TD_SECONDS(left) - GET_TD_SECONDS(right);
+ int microseconds = GET_TD_MICROSECONDS(left) -
+ GET_TD_MICROSECONDS(right);
+ result = new_delta(days, seconds, microseconds, 1);
}
if (result == Py_NotImplemented)