c++ passing arguments by reference and pointer

Question

in c++

class bar
{
    int i;
    char b;
    float d;
};

void foo ( bar arg );
void foo ( bar &arg );
void foo ( bar *arg );

this i

Answer 1

Function foo can modify arg in cases 2 and 3. In first cases compiler could optimize copy creation, so it is very hard to compare cpu and memory usage.