new DIP38: Safe references and rvalue references without runtime checks.

[Steven Schveighoffer]

On Tue, 07 May 2013 15:20:43 -0400, Jonathan M Davis <jmdavisProg at gmx.com>  
wrote:

> On Monday, May 06, 2013 23:28:40 Timothee Cour wrote:
>> Ok, I have updated and simplified the DIP38, please take a look. In
>> the proposed 'manual' scheme A, the user annotates each ref argument of  
>> a
>> ref-return function with either inref or outref (let's postpone the
>> discussion of what exactly those keywords should be and focus on the
>> logic instead; see bottom of email for a possibility). In proposed
>> scheme B, the inref/outref are instead
>> automatically infered. Let's focus on scheme A to avoid doing
>> interprocedural analysis.
>
> I confess that my gut reaction to all of this is that it's just plain  
> simpler
> to do the runtime check. It won't be needed often and is trivial to  
> disable if
> you don't want it. And it requires no annotations whatsoever. We're  
> already
> seriously pushing it with the sheer number of annotations that we have,  
> so I'm
> very much inclined to argue against adding new ones if we don't really  
> need
> them.

While I agree here, and there is the cognitive load of understanding the  
attributes to take into account, I like the proposed mechanism to  
propagate attributes to the .di file automatically for no-body functions.

That in itself would enable attribute inference, as long as developers of  
closed-source libraries agreed to use that mechanism.

-Steve