Is it possible to take a parameter by const reference, while banning conversions so that temporaries aren't passed instead?

Question

Sometimes we like to take a large parameter by reference, and also to make the reference const if possible to advertize that it is an input parameter. But by making the refe

Answer 1

You can't, and even if you could, it probably wouldn't help much. Consider:

void another(long const& l)
{
    bar_const(l);
}

Even if you could somehow prevent the binding to a temporary as input to bar_const, functions like another could be called with the reference bound to a temporary, and you'd end up in the same situation.

If you can't accept a temporary, you'll need to use a reference to a non-const, or a pointer:

void bar_const(long const* l);

requires an lvalue to initialize it. Of course, a function like

void another(long const& l)
{
    bar_const(&l);
}

will still cause problems. But if you globally adopt the convention to use a pointer if object lifetime must extend beyond the end of the call, then hopefully the author of another will think about why he's taking the address, and avoid it.