Re: Automatially move from $n (was: C++11 move semantics)

[Frank Heckenbach]

Hans Åberg wrote:

> >> Yes, indeed C++ does not support that,
> > 
> > Are you replying to your own statement now? I never claimed (or
> > cared) whether C++ supports GC.
> 
> C++ does not support the implementation of a (tracing) GC, because
> the information needed, though available to the compiler, is not
> available from the language. The fact that it does not have a GC
> is another topic.

I know and (again) I don't care because I don't want to use GC
anyway. You're basically discussing with yourself here.

> > At runtime, yes. Basically an extended unique_ptr could detect this
> > automatically.
> 
> This looks like becoming you option. You might use it for
> debugging only.

My option? I'm not having this problem. Again, I only brought up the
make_pair thing as a counterexample to your claim that an automatic
break would avoid any possible double-move.

But it might be a solution to someone else's problem (or another
problem of mine some other day ;).

> > I'd rather see a compile-time check, even if it's a
> > bit primitive, i.e. gives false positives.
> 
> Even though the compiler may have access to the information to
> check that, you don't have access to that from the language
> itself. Parsing the language is a long haul, even though there
> were some here wanting help with that.

No, I don't want to go there. As said before, I see two viable
compile-time options so far:

- Within Bison, hopefully rather easy to implement, but with some
  false positives.

- Within(!) the compiler, more general, but a job for compiler
  experts, not me.

Regards,
Frank