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Language: C++
Expertise: Beginner

May 21, 2001

Consider the code snippet below:

 
BaseClass *bp;
for(i =0;i< VERY_LARGE_NUM;i++)
  bp->VirtualFunc();

Such a situation can lead to an unacceptably high overhead of calling a virtual function. This can be remedied by converting the virtual function call in a non-virtual function call. This code fragment shows how to directly call a virtual function so as to avoid the overhead of a virtual-function-call:

 
BaseClass *bp;
if(typeid(*bp) == typeid(BaseClass))
{
     for(i =0;i< VERY_LARGE_NUM;i++)
                 bp->BaseClass::VirtualFunc();
}
else if(typeid(*bp) == typeid(DerivedClass))
{
       for(i =0;i< VERY_LARGE_NUM;i++)
                 bp->DerivedClass::VirtualFunc();
}
else
{
           for(i =0;i< VERY_LARGE_NUM;i++)
                     bp->VirtualFunc();
}