Is it better to pass by value or by reference for basic datatypes? [duplicate]

Answer 1

In the case of ordinal types — i.e. int, float, bool, etc. — there is no savings in using a reference instead of simply using pass by value. Source Source2

Answer 2

I don't see the reason why it would be faster. You need to send the parameter to the function in both case. If the function get pointer instead of value, then the pointer needs dereferencing which might be slower than sending plain value.

Answer 3

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.

Answer 4

If you use references, make them const:

void bbb(const int & a, const float & b);

Otherwise the semantics will be different from passing by value, as the function could change the value of the variables passed to the parameters. This would imply that you could not use literals for the arguments.