References in D

[Maxim Fomin]

On Saturday, 15 September 2012 at 13:49:02 UTC, Simen Kjaeraas 
wrote:
>> void foo(ref S s); // cannot pass null pointer S* or null - 
>> "always there"
>
> void bar( ref int n ) {
>     n = 3;
> }
>
> void main( ) {
>     int* p = null;
>     bar( *p );
> }
>
> Good luck.
>
> Of course, it's not that obvious in production code, but I've 
> had this
> happen to me in C++, and - obviously - it can happen in D, too.

The problem happens because you deliberately passed hidden null 
pointer. And in real code it could crash after dereferencing and 
before passing to bar, if accessed (meaning that problem is in 
erroneous pointer usage, not accepting ints through reference in 
bar). Certainly, it is possible to break even in such cases, as 
well as in other parts of the language which doesn't necessarily 
mean that such parts of the language are broken. What I was 
talking about is:

void bar( ref int n ) {
     n = 3;
}

void main( ) {
     int* p = null;
     bar(p); // error
     bar(null); //error
}