Non-psychic debugging: If somebody's complaining that a collection should be empty but isn't, you might want to see what's in there
A programmer on the GHI team(yes,the same GHI team)reported that they were hitting an assertion failureusing an internal library and asked for help debugging it.
// All factories should be unregistered by now assert(m_pFactoryList->IsEmpty());
“Can somebody help me figure out which factory it is thatdid not get unregistered?”
I didn’t work on this internal library, but on the other handI’m not afraid to look inside.
Let’s see what a
m_pFactoryList looks like.
0:000> ?? this->m_pFactoryList class LookupTable<CFactory*> +0x000 m_uListSize : 1 // this probably means that the list has one element +0x004 m_pList : 0x00212e60 LookupTable<CFactory*>::ENTRY // this is probably the list +0x008 m_uCapacity : 0x7f 0:000> ?? this->m_pFactoryList->m_pList struct LookupTable<CFactory*>::ENTRY * 0x00212e60 +0x000 pszName : 0x02cf4048 "GHI_factory" +0x004 data : 0x02cf4ce0 CFactory* // I bet this is the item that got leaked 0:000> dps 0x02cf4ce0 l1 02cf4ce0 6b626d58 GHI!CGhiFactory::`vftable`
No psychic powers needed here.I just followed my nose.
The assertion says that a list is not empty.Therefore, we should look to see what is on the list.
As a general rule, code is not intentionally written to beimpossible to understand.The person who wrote it meant well,so if you see a member called
m_uListSize, it’s a pretty safe bet that itrepresents the list size.And if you see a member called
m_pList,it probably points to the start of the list.