Re: RFD - cleaning up C identifier lookup

[Zack Weinberg <zack at codesourcery dot com>]

Gabriel Dos Reis <gdr at integrable-solutions dot net> writes:

> Zack Weinberg <zack at codesourcery dot com> writes:
...
> | struct lang_identifier GTY(())
> | {
> |   struct c_common_identifier common_id;
> |   tree symbol_value;
> |   tree tag_value;
> |   tree label_value;
> | }
...
> | Much of this stuff could also be applied to the C++ front end also,
>
> That might; but in fact, that would be a complication (and hardly an
> improvement over current situation) for C++. 
>
> A distinction is that C++ has a single name space  as opposed to C.
> An immediate consequence is that the C++ front-end would have to jump
> through whoops to ensure that we can C++ semantics right.

By this you mean that symbols and tags occupy the same namespace,
right?  6.1p1 [stmt.label] says that labels have their own namespace,
so I think you'd still need the pointer for that.  (However, labels
are rare enouugh that it might be worthwhile to use a separate table
for them, saving more space in the identifier.)


> The route I take on this issue for C++ is to get rid of the confusion
> notions of binding-level and scope in G++.  Instead, I just use the
> standard notion of scope and implement essentially 
>
>   1) local scopes (these are blocks) with the refinements:
>        + try-scope
>        + catch-scope
>        + for-while scope
>   2) function prototype scopes
>   3) class scope
>   4) namespace scope
>   5) template prototype scope

C99 has for-while scope and function-prototype scope, too.  And
there's also file scope.

I'd like to do something compatible with merging the C and C++ front
ends in the future, and I can see getting rid of the binding-level
concept as worthwhile for C too (but I want to do this incrementally).
I don't think the conflicts here are severe.  What would you suggest I
do to bring things into congruence?

>     struct lang_identifier GTY(())
>     {
>       struct c_common_identifier c_common;
>       tree class_template_info;
>       struct lang_id2 *x;
>     };

What's in a struct lang_id2?

zw