Problem with template...

Jean-Sebastien Vachon
Thu Sep 12 05:36:00 GMT 2002


One of my co-worker has developped a template to instantiate a HashTable
and until recently everything was fine.

However, in the last few days he added a simple line (legitimate) that
cause all kind of problems on Linux but runs fine on Windows (I don't
know for other Unixes)

Here is the code...

template <class T_Key, class T_HashObj> 
void HashTable<T_Key, T_HashObj>::Remove(T_Key oHKey, T_HashObj* poHObj)
    int nHash = Hash(oHKey);

    if (mpapoHashBuckets[nHash])
	HashElement* poHsbl = NULL;
	BucketObject*  poDelete = NULL;
	BucketObject*  poCurrent = 
	    (BucketObject *) mpapoHashBuckets[nHash]->GetHead();

	while (poCurrent)
	    poDelete = poCurrent;
	    poHsbl = (HashElement *) poCurrent->GetObj();
	    poCurrent = poCurrent->GetNext();		
	    if (poHsbl && 
		mfEqualFnctn(poHsbl->GetKey(), oHKey) && 
		poHsbl->GetHashObjRef() == poHObj)
		HDelete poHsbl;
		poHsbl = NULL;
		mnHashObjs--;		// <==== NEW LINE

I don't know why but when I step in the code down to this point and then
look at the execution step by step.. the new line is executed twice.

poCurrent starts with a valid pointer and poCurrent->GetNext() returns
NULL. The if (within the while) is executed as it should but when the
while condition is evaluated a second time, it jumps to NEW LINE before
exiting the function.

I tried reorganising the while loop but the problem is still there.

Any idea? 

I am using GCC 3.1 on a i686-Linux (RedHat 7.2) system. The debugger I
used to step into the code is the latest release of GDB (5.2.1 installed

Thanks for you time.

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