/*
 * get a list of guids
 * for each guid
 *    if it is not GUID_NULL
 *       do stuff
 */
vector<GUID> guids = getGuids();
for (vector<GUID>::iterator i = guids.begin(); i != guids.end() && *i != GUID_NULL; i++)
{
     // do stuff
}

I wrote the above code that meant to achieve the result in the pseudo code. Surprisingly (or fortunately) my testing code failed. I should not have evaluated the GUID_NULL condition in the loop-test. So here is the corrected code.

vector<GUID>: guids = getGuids();
for (vector<GUID>:::iterator i = guids.begin(); i != guids.end(); i++)
{
    if (*i != GUID_NULL)
        // do stuff
}

well, this was a very basic logic error, I could only blame my hurting brain after a long day of coding. anyway, unit testing rocks.