Is there a way to make passing by reference, and passing by value explicit in the function call?

Question

If you were to look at this code,

int x = 0;
function(x);
std::cout << x << \'\\n\';

you would not be able to verify through any me

Answer 1

I'm not sure I understand your requirements completely, but maybe this is something you can use:

template
void foo( T ) { static_assert( sizeof(T)==0, "foo() requires a std::ref" ); }

void foo( std::reference_wrapper t )
{
    // modify i here via t.get() or other means of std::reference_wrapper
}

int main()
{
    int i = 42;
    // foo( i ); // does not compile, static_assert fires
    foo( std::ref( i ) ); // explicit std::ref visible on the caller's side
}