Clear errors raised by PyObject_Compare() without losing any existing

exception context.  This avoids improperly propogating errors raised by
a user-defined __cmp__() by a subsequent lookup operation.

This patch does *not* include the performance enhancement patch for
dictionaries with string keys only; that will be checked in separately.

This closes SourceForge patch #101277 and bug #112558.

diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index ddd8eb8b69d46a0bbcc5ed8847a4628ff6003dba..621ed736381282f43ab6cdf7663105ed6ba77ca5 100644 (file)
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -139,6 +139,10 @@ lookdict(dictobject *mp, PyObject *key, register long hash)
        register unsigned int mask = mp->ma_size-1;
        dictentry *ep0 = mp->ma_table;
        register dictentry *ep;
+       register int restore_error = 0;
+       register int checked_error = 0;
+       register int cmp;
+       PyObject *err_type, *err_value, *err_tb;
        /* We must come up with (i, incr) such that 0 <= i < ma_size
           and 0 < incr < ma_size and both are a function of hash */
        i = (~hash) & mask;
@@ -151,14 +155,25 @@ lookdict(dictobject *mp, PyObject *key, register long hash)
        if (ep->me_key == dummy)
                freeslot = ep;
        else {
-               if (ep->me_hash == hash &&
-                   PyObject_Compare(ep->me_key, key) == 0)
-               {
-                       return ep;
+               if (ep->me_hash == hash) {
+                       /* error can't have been checked yet */
+                       checked_error = 1;
+                       if (PyErr_Occurred()) {
+                               restore_error = 1;
+                               PyErr_Fetch(&err_type, &err_value, &err_tb);
+                       }
+                       cmp = PyObject_Compare(ep->me_key, key);
+                       if (PyErr_Occurred())
+                               PyErr_Clear();
+                       else if (cmp == 0) {
+                               if (restore_error)
+                                       PyErr_Restore(err_type, err_value,
+                                                     err_tb);
+                               return ep;
+                       }
                }
                freeslot = NULL;
        }
-       /* XXX What if PyObject_Compare returned an exception? */
        /* Derive incr from hash, just to make it more arbitrary. Note that
           incr must not be 0, or we will get into an infinite loop.*/
        incr = (hash ^ ((unsigned long)hash >> 3)) & mask;
@@ -167,6 +182,8 @@ lookdict(dictobject *mp, PyObject *key, register long hash)
        for (;;) {
                ep = &ep0[(i+incr)&mask];
                if (ep->me_key == NULL) {
+                       if (restore_error)
+                               PyErr_Restore(err_type, err_value, err_tb);
                        if (freeslot != NULL)
                                return freeslot;
                        else
@@ -176,12 +193,30 @@ lookdict(dictobject *mp, PyObject *key, register long hash)
                        if (freeslot == NULL)
                                freeslot = ep;
                }
-               else if (ep->me_key == key ||
-                        (ep->me_hash == hash &&
-                         PyObject_Compare(ep->me_key, key) == 0)) {
+               else if (ep->me_key == key) {
+                       if (restore_error)
+                               PyErr_Restore(err_type, err_value, err_tb);
                        return ep;
+                }
+                else if (ep->me_hash == hash) {
+                       if (!checked_error) {
+                               checked_error = 1;
+                               if (PyErr_Occurred()) {
+                                       restore_error = 1;
+                                       PyErr_Fetch(&err_type, &err_value,
+                                                   &err_tb);
+                               }
+                       }
+                       cmp = PyObject_Compare(ep->me_key, key);
+                       if (PyErr_Occurred())
+                               PyErr_Clear();
+                       else if (cmp == 0) {
+                               if (restore_error)
+                                       PyErr_Restore(err_type, err_value,
+                                                     err_tb);
+                               return ep;
+                       }
                }
-               /* XXX What if PyObject_Compare returned an exception? */
                /* Cycle through GF(2^n)-{0} */
                incr = incr << 1;
                if (incr > mask)