Getting a reference to an immutable string

[David Zhang via Digitalmars-d-learn]

Hi,

I've got an immutable string declared in module scope, and I 
attempted to get a pointer to its characters through both &str[0] 
and str.ptr. However, it appears to me that the string is 
behaving like a manifest constant, in that the pointer is null.

The language reference indicates that it has a location in memory 
and thus has a pointer.

So, my question is thus: Is this a bug in DMD, or is this just 
something I missed?

Thanks

David