How are arrays passed?

Question

Are arrays passed by default by ref or value? Thanks.

Answer 1

First, you cannot pass an array by value in the sense that a copy of the array is made. If you need that functionality, use std::vector or boost::array.

Normally, a pointer to the first element is passed by value. The size of the array is lost in this process and must be passed separately. The following signatures are all equivalent:

void by_pointer(int *p, int size);
void by_pointer(int p[], int size);
void by_pointer(int p[7], int size);   // the 7 is ignored in this context!

If you want to pass by reference, the size is part of the type:

void by_reference(int (&a)[7]);   // only arrays of size 7 can be passed here!

Often you combine pass by reference with templates, so you can use the function with different statically known sizes:

template
void by_reference(int (&a)[size]);

Hope this helps.