Make sure that all ints, even internal, temporary ones, have at least…

… one digit.
python · markshannon · Aug 25, 2021 · Aug 18, 2021 · Aug 19, 2021 · Aug 19, 2021
commit 0533a9f891f0c54616eef369239cd6554972816f
diff --git a/Objects/longobject.c b/Objects/longobject.c
@@ -124,18 +124,21 @@ PyLongObject *
 _PyLong_New(Py_ssize_t size)
 {
     PyLongObject *result;
-    /* Number of bytes needed is: offsetof(PyLongObject, ob_digit) +
-       sizeof(digit)*size.  Previous incarnations of this code used
-       sizeof(PyVarObject) instead of the offsetof, but this risks being
-       incorrect in the presence of padding between the PyVarObject header
-       and the digits. */
     if (size > (Py_ssize_t)MAX_LONG_DIGITS) {
         PyErr_SetString(PyExc_OverflowError,
                         "too many digits in integer");
         return NULL;
     }
+    /* Fast operations for single digit integers (including zero)
+     * assume that there is always at least one digit present. */
+    Py_ssize_t ndigits = size ? size : 1;
+    /* Number of bytes needed is: offsetof(PyLongObject, ob_digit) +
+       sizeof(digit)*size.  Previous incarnations of this code used
+       sizeof(PyVarObject) instead of the offsetof, but this risks being
+       incorrect in the presence of padding between the PyVarObject header
+       and the digits. */
     result = PyObject_Malloc(offsetof(PyLongObject, ob_digit) +
-                             size*sizeof(digit));
+                             ndigits*sizeof(digit));
     if (!result) {
         PyErr_NoMemory();
         return NULL;