[M3devel] ADR is *too* unsafe..

[Tony Hosking]

Also, I meant to point to:

http://www.modula3.org/threads/3/#advancedTopic

On 2 Jun 2010, at 11:02, Tony Hosking wrote:

> Actually, the compiler already has support to do exactly what you want.  Take a look at the flag Host.new_adr.  This implements:
> 
> ADR (t: T): UNTRACED REF T
> 
> 
> 
> On 2 Jun 2010, at 10:07, Jay K wrote:
> 
>> 
>> The compiler doesn't break. Mentor does, networking stuff. I fixed it. But I would have
>> expected the compiler to have told me about it.
>> It is unfortunate. ADR should be *slightly* safer.
>> Maybe we can get a warning for this? passing ADR(foo) to untraced ref bar?
>> It seems...quite unfortunate that the language is defined this way..
>> 
>> - Jay
>> 
>> 
>> ----------------------------------------
>>> From: hosking at cs.purdue.edu
>>> Date: Wed, 2 Jun 2010 10:01:09 -0400
>>> To: jay.krell at cornell.edu
>>> CC: m3devel at elegosoft.com
>>> Subject: Re: [M3devel] ADR is *too* unsafe..
>>> 
>>> 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
>>>> 
>>> 
>> 		 	   		  
>