[M3devel] ADR is *too* unsafe..

[Tony Hosking]

Why does the compiler break?
Yes, VAR is *much* safer.

On 2 Jun 2010, at 03:41, Jay K wrote:

> 
> (*
> Wow, ADR generates a plain ADDRESS, not an untraced ref to a specific type?
> Doesn't this seem wrong? Doesn't unsafe code deserve a little better, say,
>   to be at least as typesafe as C?
> http://www.cs.purdue.edu/homes/hosking/m3/reference/unsafe.html
> 
> This is why 64bit m3-comm/tcp/src/TCP.m3 breaks randomly
> on some platforms on an assertion failure in C. And the
> compiler isn't going to help me find these type mismatches? Ugh.
> 
> This seems wrong. :(
> 
> I guess I should really really use VAR then.
> *)
> 
> 
> UNSAFE MODULE Main;
> IMPORT Ctypes, Cstddef;
> 
> 
> PROCEDURE F1(a:UNTRACED REF Ctypes.int) =
> BEGIN
>   F2(a); (* error, expected *)
> END F1;
> 
> 
> PROCEDURE F2(a:UNTRACED REF Cstddef.size_t) =
> BEGIN
>   F1(a); (* error, expected *)
> END F2;
> 
> 
> VAR c:Ctypes.int;
>     d:Cstddef.size_t;
> 
>     
> BEGIN
>   F1(ADR(c)); (* ok *)
>   F1(ADR(d)); (* error expected but no *)
>   F2(ADR(c)); (* error expected but no *)
>   F2(ADR(d)); (* ok *)
> END Main.
> 
> 
> 
>  - Jay
>