Re: generalized lvalues -- patch outline

[Ziemowit Laski <zlaski at apple dot com>]

On 22 Nov 2004, at 13.01, Nathan Sidwell wrote:

> Ziemowit Laski wrote:
> > Indeed, I now appear to have a mainline mod for C and C++ which 
> > allows assignment to lvalue casts for pointer types.  What follows is 
> > a high-level synopsis of what I did; if there is interest, I can whip 
> > up a full-fledged patch, complete with docs.  Please let me know.
>
> Please describe the semantics *in detail* of what you are trying to
> achieve.  Why are the modify-assignment operators not allowed? That
> appears non-orthogonal.

Modify-assignment is (or should be; I'll check) allowed.

The semantics are that a C-style cast of an lvalue will itself be 
treated as an lvalue under the following circumstances:
  - The lvalue cast does not induce a type conversion (if it does, then 
we use the type conversion instead);
  - The lvalue cast is being assigned to, incremented or decremented;
  - The lvalue is of a pointer type, and is being cast to a pointer 
type.  (This will need to be relaxed somewhat should people desire 
Microsoft compatibility, at least for C.)

Of course, all of this only with the -flvalue-cast-assign flag 
specified.

--Zem