Refactor PyLongObject into object header and PyLongValue struct.

python · markshannon · Jan 30, 2023 · Jan 24, 2023 · Jan 24, 2023 · Jan 24, 2023
commit 0ea6bff0b487b9426aa1403a4ff1133fea2f5763
diff --git a/Include/cpython/longintrepr.h b/Include/cpython/longintrepr.h
@@ -71,17 +71,19 @@ typedef long stwodigits; /* signed variant of twodigits */
         0 <= ob_digit[i] <= MASK.
    The allocation function takes care of allocating extra memory
    so that ob_digit[0] ... ob_digit[abs(ob_size)-1] are actually available.
-   We always allocate memory for at least one digit, so accessing ob_digit[0]
-   is always safe. However, in the case ob_size == 0, the contents of
-   ob_digit[0] may be undefined.
 
    CAUTION:  Generic code manipulating subtypes of PyVarObject has to
    aware that ints abuse  ob_size's sign bit.
 */
 
-struct _longobject {
-    PyObject_VAR_HEAD
+typedef struct _PyLongValue {
+    Py_ssize_t ob_size; /* Number of items in variable part */
     digit ob_digit[1];
+} _PyLongValue;
+
+struct _longobject {
+    PyObject_HEAD
+    _PyLongValue long_value;
 };
 
 PyAPI_FUNC(PyLongObject *) _PyLong_New(Py_ssize_t);

@@ -149,9 +149,11 @@ extern "C" {
 
 #define _PyLong_DIGIT_INIT(val) \
     { \
-        _PyVarObject_IMMORTAL_INIT(&PyLong_Type, \
-                                   ((val) == 0 ? 0 : ((val) > 0 ? 1 : -1))), \
-        .ob_digit = { ((val) >= 0 ? (val) : -(val)) }, \
+        .ob_base = _PyObject_IMMORTAL_INIT(&PyLong_Type), \
+        .long_value  = { \
+            ((val) == 0 ? 0 : ((val) > 0 ? 1 : -1)), \
+            { ((val) >= 0 ? (val) : -(val)) }, \
+        } \
     }
 
 #define _PyBytes_SIMPLE_INIT(CH, LEN) \

diff --git a/Modules/_decimal/_decimal.c b/Modules/_decimal/_decimal.c
@@ -2171,16 +2171,16 @@ dec_from_long(PyTypeObject *type, PyObject *v,
     }
 
     if (len == 1) {
-        _dec_settriple(dec, sign, *l->ob_digit, 0);
+        _dec_settriple(dec, sign, *l->long_value.ob_digit, 0);
         mpd_qfinalize(MPD(dec), ctx, status);
         return dec;
     }
 
 #if PYLONG_BITS_IN_DIGIT == 30
-    mpd_qimport_u32(MPD(dec), l->ob_digit, len, sign, PyLong_BASE,
+    mpd_qimport_u32(MPD(dec), l->long_value.ob_digit, len, sign, PyLong_BASE,
                     ctx, status);
 #elif PYLONG_BITS_IN_DIGIT == 15
-    mpd_qimport_u16(MPD(dec), l->ob_digit, len, sign, PyLong_BASE,
+    mpd_qimport_u16(MPD(dec), l->long_value.ob_digit, len, sign, PyLong_BASE,
                     ctx, status);
 #else
   #error "PYLONG_BITS_IN_DIGIT should be 15 or 30"
@@ -3543,11 +3543,11 @@ dec_as_long(PyObject *dec, PyObject *context, int round)
         return NULL;
     }
 
-    memcpy(pylong->ob_digit, ob_digit, n * sizeof(digit));
+    memcpy(pylong->long_value.ob_digit, ob_digit, n * sizeof(digit));
     mpd_free(ob_digit);
 
     i = n;
-    while ((i > 0) && (pylong->ob_digit[i-1] == 0)) {
+    while ((i > 0) && (pylong->long_value.ob_digit[i-1] == 0)) {
         i--;
     }
 

diff --git a/Objects/boolobject.c b/Objects/boolobject.c
@@ -195,11 +195,11 @@ PyTypeObject PyBool_Type = {
 /* The objects representing bool values False and True */
 
 struct _longobject _Py_FalseStruct = {
-    PyVarObject_HEAD_INIT(&PyBool_Type, 0)
-    { 0 }
+    PyObject_HEAD_INIT(&PyBool_Type)
+    { 0, { 0 } }
 };
 
 struct _longobject _Py_TrueStruct = {
-    PyVarObject_HEAD_INIT(&PyBool_Type, 1)
-    { 1 }
+    PyObject_HEAD_INIT(&PyBool_Type)
+    { 1, { 1 } }
 };
diff --git a/Objects/listobject.c b/Objects/listobject.c
@@ -2155,8 +2155,8 @@ unsafe_long_compare(PyObject *v, PyObject *w, MergeState *ms)
     vl = (PyLongObject*)v;
     wl = (PyLongObject*)w;
 
-    v0 = Py_SIZE(vl) == 0 ? 0 : (sdigit)vl->ob_digit[0];
-    w0 = Py_SIZE(wl) == 0 ? 0 : (sdigit)wl->ob_digit[0];
+    v0 = Py_SIZE(vl) == 0 ? 0 : (sdigit)vl->long_value.ob_digit[0];
+    w0 = Py_SIZE(wl) == 0 ? 0 : (sdigit)wl->long_value.ob_digit[0];
 
     if (Py_SIZE(vl) < 0)
         v0 = -v0;