2010/2/9 Teodor Sigaev <teodor@sigaev.ru>:
>>> Good idea, implemented.
>>
>> Hmm. I think your implementation is prone to overflow in two places -
>> both when computing step, and also when stepping through the array.
>
> Pls, point me, I don't see that
> ! step |= (step >> 1);
> ! step |= (step >> 2);
> ! step |= (step >> 4);
> ! step |= (step >> 8);
> ! step |= (step >> 16);
So suppose at this point that step is the largest integer that can be
represented...
> ! step ++;
Boom.
> ! step >>= 1;
> !
> ! while(step > 0) {
> ! int i;
>
> ! for (i = step-1; i < nentry; i += 2 * step)
And similarly here... if nentry is greater than maxint/2, then i += 2
* step will overflow, no?
> ! ginInsertEntry(accum, heapptr, attnum, entries[i]);
>
> ! step >>= 1; /* /2 */
> ! }
>
>
>> Proposed revision attached, with also some rewriting of the comment
>> for that function.
>
> make check fails with your patch:
>
> #3 0x083d2b50 in ExceptionalCondition (conditionName=Could not find the
> frame base for "ExceptionalCondition".
> ) at assert.c:57
> #4 0x081086b6 in ginAppendData (old=0x287f2030, new=0x287f2044,
> arg=0xbfbfd5e4) at ginbulk.c:48
> #5 0x083f5632 in rb_insert (rb=0x2acfe610, data=0x287f2044) at rbtree.c:359
> #6 0x08108968 in ginInsertEntry (accum=0xbfbfd5e4, heapptr=0x28711af4,
> attnum=1, entry=2139062143) at ginbulk.c:135
> #7 0x08108ad9 in ginInsertRecordBA (accum=0xbfbfd5e4, heapptr=0x28711af4,
> attnum=1, entries=0x2ac77068, nentry=6) at ginbulk.c:202
Gaah, sorry. Presumably I'm running off the end of the array, though
I don't see what I did wrong. My brain is fried.
...Robert
