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Implement the intention of SF patch 472523 (but coded differently). 

In the past, an object's tp_compare could return any value.  In 2.2
the docs were tightened to require it to return -1, 0 or 1; and -1 for
an error.

We now issue a warning if the value is not in this range.  When an
exception is raised, we allow -1 or -2 as return value, since -2 will
the recommended return value for errors in the future.  (Eventually
tp_compare will also be allowed to return +2, to indicate
NotImplemented; but that can only be implemented once we know all
extensions return a value in [-2...1].  Or perhaps it will require the
type to set a flag bit.)

I haven't decided yet whether to backport this to 2.2.x.  The patch
applies fine.  But is it fair to start warning in 2.2.2 about code
that worked flawlessly in 2.2.1?
This commit is contained in:
Guido van Rossum 2002-05-31 20:03:54 +00:00
parent 32a7e7f6b6
commit a407300cd7
1 changed files with 66 additions and 14 deletions
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80
Objects/object.c
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@ -353,6 +353,46 @@ PyObject_Unicode(PyObject *v)
#endif
/* Helper to warn about deprecated tp_compare return values. Return:
-2 for an exception;
-1 if v < w;
0 if v == w;
1 if v > w.
(This function cannot return 2.)
*/
static int
adjust_tp_compare(int c)
{
if (PyErr_Occurred()) {
if (c != -1 && c != -2) {
PyObject *t, *v, *tb;
PyErr_Fetch(&t, &v, &tb);
if (PyErr_Warn(PyExc_RuntimeWarning,
"tp_compare didn't return -1 or -2 "
"for exception") < 0) {
Py_XDECREF(t);
Py_XDECREF(v);
Py_XDECREF(tb);
}
else
PyErr_Restore(t, v, tb);
}
return -2;
}
else if (c < -1 || c > 1) {
if (PyErr_Warn(PyExc_RuntimeWarning,
"tp_compare didn't return -1, 0 or 1") < 0)
return -2;
else
return c < -1 ? -1 : 1;
}
else {
assert(c >= -1 && c <= 1);
return c;
}
}
/* Macro to get the tp_richcompare field of a type if defined */
#define RICHCOMPARE(t) (PyType_HasFeature((t), Py_TPFLAGS_HAVE_RICHCOMPARE) \
? (t)->tp_richcompare : NULL)
@ -480,9 +520,7 @@ try_3way_compare(PyObject *v, PyObject *w)
/* If both have the same (non-NULL) tp_compare, use it. */
if (f != NULL && f == w->ob_type->tp_compare) {
c = (*f)(v, w);
if (c < 0 && PyErr_Occurred())
return -1;
return c < 0 ? -1 : c > 0 ? 1 : 0;
return adjust_tp_compare(c);
}
/* If either tp_compare is _PyObject_SlotCompare, that's safe. */
@ -502,9 +540,7 @@ try_3way_compare(PyObject *v, PyObject *w)
c = (*f)(v, w);
Py_DECREF(v);
Py_DECREF(w);
if (c < 0 && PyErr_Occurred())
return -2;
return c < 0 ? -1 : c > 0 ? 1 : 0;
return adjust_tp_compare(c);
}
/* Try w's comparison, if defined */
@ -512,9 +548,11 @@ try_3way_compare(PyObject *v, PyObject *w)
c = (*f)(w, v); /* swapped! */
Py_DECREF(v);
Py_DECREF(w);
if (c < 0 && PyErr_Occurred())
return -2;
return c < 0 ? 1 : c > 0 ? -1 : 0; /* negated! */
c = adjust_tp_compare(c);
if (c >= -1)
return -c; /* Swapped! */
else
return c;
}
/* No comparison defined */
@ -591,11 +629,11 @@ default_3way_compare(PyObject *v, PyObject *w)
#define CHECK_TYPES(o) PyType_HasFeature((o)->ob_type, Py_TPFLAGS_CHECKTYPES)
/* Do a 3-way comparison, by hook or by crook. Return:
-2 for an exception;
-2 for an exception (but see below);
-1 if v < w;
0 if v == w;
1 if v > w;
If the object implements a tp_compare function, it returns
BUT: if the object implements a tp_compare function, it returns
whatever this function returns (whether with an exception or not).
*/
static int
@ -607,9 +645,22 @@ do_cmp(PyObject *v, PyObject *w)
if (v->ob_type == w->ob_type
&& (f = v->ob_type->tp_compare) != NULL) {
c = (*f)(v, w);
if (c != 2 || !PyInstance_Check(v))
return c;
if (PyInstance_Check(v)) {
/* Instance tp_compare has a different signature.
But if it returns undefined we fall through. */
if (c != 2)
return c;
/* Else fall throug to try_rich_to_3way_compare() */
}
else
return adjust_tp_compare(c);
}
/* We only get here if one of the following is true:
a) v and w have different types
b) v and w have the same type, which doesn't have tp_compare
c) v and w are instances, and either __cmp__ is not defined or
__cmp__ returns NotImplemented
*/
c = try_rich_to_3way_compare(v, w);
if (c < 2)
return c;
@ -902,7 +953,8 @@ PyObject_RichCompare(PyObject *v, PyObject *w, int op)
fcmp = v->ob_type->tp_compare;
if (fcmp != NULL) {
int c = (*fcmp)(v, w);
if (c < 0 && PyErr_Occurred()) {
c = adjust_tp_compare(c);
if (c == -2) {
res = NULL;
goto Done;
}