bpo-41710: Add _PyTime_AsTimespec_clamp() (GH-28629)

Add the _PyTime_AsTimespec_clamp() function: similar to
_PyTime_AsTimespec(), but clamp to _PyTime_t min/max and don't raise
an exception.

PyThread_acquire_lock_timed() now uses _PyTime_AsTimespec_clamp() to
remove the Py_UNREACHABLE() code path.

* Add _PyTime_AsTime_t() function.
* Add PY_TIME_T_MIN and PY_TIME_T_MAX constants.
* Replace _PyTime_AsTimeval_noraise() with _PyTime_AsTimeval_clamp().
* Add pytime_divide_round_up() function.
* Fix integer overflow in pytime_divide().
* Add pytime_divmod() function.

4 files changed, 47 insertions, 4 deletions

diff --git a/Modules/_ssl.c b/Modules/_ssl.c
index 6c63301..411314f 100644
--- a/Modules/_ssl.c
+++ b/Modules/_ssl.c
@@ -2264,7 +2264,7 @@ PySSL_select(PySocketSockObject *s, int writing, _PyTime_t timeout)
     if (!_PyIsSelectable_fd(s->sock_fd))
         return SOCKET_TOO_LARGE_FOR_SELECT;
 
-    _PyTime_AsTimeval_noraise(timeout, &tv, _PyTime_ROUND_CEILING);
+    _PyTime_AsTimeval_clamp(timeout, &tv, _PyTime_ROUND_CEILING);
 
     FD_ZERO(&fds);
     FD_SET(s->sock_fd, &fds);
diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index 51323f0..e3eec0c 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -4687,7 +4687,32 @@ test_PyTime_AsTimeval(PyObject *self, PyObject *args)
     if (seconds == NULL) {
         return NULL;
     }
-    return Py_BuildValue("Nl", seconds, tv.tv_usec);
+    return Py_BuildValue("Nl", seconds, (long)tv.tv_usec);
+}
+
+static PyObject *
+test_PyTime_AsTimeval_clamp(PyObject *self, PyObject *args)
+{
+    PyObject *obj;
+    int round;
+    if (!PyArg_ParseTuple(args, "Oi", &obj, &round)) {
+        return NULL;
+    }
+    if (check_time_rounding(round) < 0) {
+        return NULL;
+    }
+    _PyTime_t t;
+    if (_PyTime_FromNanosecondsObject(&t, obj) < 0) {
+        return NULL;
+    }
+    struct timeval tv;
+    _PyTime_AsTimeval_clamp(t, &tv, round);
+
+    PyObject *seconds = PyLong_FromLongLong(tv.tv_sec);
+    if (seconds == NULL) {
+        return NULL;
+    }
+    return Py_BuildValue("Nl", seconds, (long)tv.tv_usec);
 }
 
 #ifdef HAVE_CLOCK_GETTIME
@@ -4708,6 +4733,22 @@ test_PyTime_AsTimespec(PyObject *self, PyObject *args)
     }
     return Py_BuildValue("Nl", _PyLong_FromTime_t(ts.tv_sec), ts.tv_nsec);
 }
+
+static PyObject *
+test_PyTime_AsTimespec_clamp(PyObject *self, PyObject *args)
+{
+    PyObject *obj;
+    if (!PyArg_ParseTuple(args, "O", &obj)) {
+        return NULL;
+    }
+    _PyTime_t t;
+    if (_PyTime_FromNanosecondsObject(&t, obj) < 0) {
+        return NULL;
+    }
+    struct timespec ts;
+    _PyTime_AsTimespec_clamp(t, &ts);
+    return Py_BuildValue("Nl", _PyLong_FromTime_t(ts.tv_sec), ts.tv_nsec);
+}
 #endif
 
 static PyObject *
@@ -5872,8 +5913,10 @@ static PyMethodDef TestMethods[] = {
     {"PyTime_FromSecondsObject", test_pytime_fromsecondsobject,  METH_VARARGS},
     {"PyTime_AsSecondsDouble", test_pytime_assecondsdouble, METH_VARARGS},
     {"PyTime_AsTimeval", test_PyTime_AsTimeval, METH_VARARGS},
+    {"PyTime_AsTimeval_clamp", test_PyTime_AsTimeval_clamp, METH_VARARGS},
 #ifdef HAVE_CLOCK_GETTIME
     {"PyTime_AsTimespec", test_PyTime_AsTimespec, METH_VARARGS},
+    {"PyTime_AsTimespec_clamp", test_PyTime_AsTimespec_clamp, METH_VARARGS},
 #endif
     {"PyTime_AsMilliseconds", test_PyTime_AsMilliseconds, METH_VARARGS},
     {"PyTime_AsMicroseconds", test_PyTime_AsMicroseconds, METH_VARARGS},
diff --git a/Modules/selectmodule.c b/Modules/selectmodule.c
index 3ecd0c3..b71b2c4 100644
--- a/Modules/selectmodule.c
+++ b/Modules/selectmodule.c
@@ -344,7 +344,7 @@ select_select_impl(PyObject *module, PyObject *rlist, PyObject *wlist,
                 n = 0;
                 break;
             }
-            _PyTime_AsTimeval_noraise(timeout, &tv, _PyTime_ROUND_CEILING);
+            _PyTime_AsTimeval_clamp(timeout, &tv, _PyTime_ROUND_CEILING);
             /* retry select() with the recomputed timeout */
         }
     } while (1);
diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
index 83f05b7..f474869 100644
--- a/Modules/socketmodule.c
+++ b/Modules/socketmodule.c
@@ -758,7 +758,7 @@ internal_select(PySocketSockObject *s, int writing, _PyTime_t interval,
     Py_END_ALLOW_THREADS;
 #else
     if (interval >= 0) {
-        _PyTime_AsTimeval_noraise(interval, &tv, _PyTime_ROUND_CEILING);
+        _PyTime_AsTimeval_clamp(interval, &tv, _PyTime_ROUND_CEILING);
         tvp = &tv;
     }
     else