Question

Possible Duplicates:
How to pass objects to functions in C++?
is there any specific case where pass-by-value is preferred over pass-by-const-reference in C++?

I have members of a class implemented like this:

void aaa(int a, float b, short c)
{
  bbb(a, b);
}

void bbb(int a, float b)
{}

If the values of a, b and c were stored in my class as constants, then would it have been better/sensible to use my functions as shown below or as shown above?

void aaa(int& a, float& b, short& c)
void bbb(int& a, float& b)

Does using references give any speed benefits or advantages in this case? Any disadvantages/overheads of references here?

Answer 1

Standard doesn’t have constraints about implementation of references, however usually they’re implemented as autodereferenced pointers (actually with some exceptions). As you probably know, on 32 bit system pointer size is 4 bytes, that means that passing chars, shorts (types with sizeof() less than 4 bytes) by reference maybe considered as somewhat overkilling – using 4 bytes instead of 1 (char) or 2 (short).
In general it depends on whether the rigisters or stack is used for passing parameters: you can save a bit of stack when passing basic types by value, but in case of registers even for chars, 4 bytes will be used, so there’s no point in trying to optimize something with ptrs/refs.