Walter is right about transitive readonly - here's the alternative

[Steven Schveighoffer]

"Janice Caron" wrote
> But worse, either the thread ID variable would be unused in release
> mode, wasting space, or it would be absent in release mode, making the
> ABI different, and hence making release and debug object files
> mutually unlinkable. Tough choice!

Hm... actually, I realize that this isn't the worst part.  The worst part is 
that if you store which threads have a shared object read-locked, then this 
becomes a LIST of threads, since multiple threads can read-lock, and so 
instead of a reference count, you have a dynamic array.  UGH!

nevermind (puts magic bullet back in pocket)

-Steve