[cfe-dev] Unneeded declarations invalidation

[Abramo Bagnara]

Daniel Dunbar ha scritto:
> On Tue, Jul 21, 2009 at 9:28 AM, Douglas Gregor<dgregor at apple.com> wrote:
>> On Jul 21, 2009, at 7:58 AM, Abramo Bagnara wrote:
>>> Douglas Gregor ha scritto:
>>> The problem we have is to avoid that AST is missing some parts of what
>>> GCC is able to compile. Do you think it will be feasible in some way?
>>>
>>> Do you have some hints for a patch that you would be willing to accept
>>> to accomplish that?
>>
>> I'm not sure how to proceed. Unfortunately, this is one of two GNU C
>> extensions I can think of that Clang will *not* support (the other is
>> nested functions), and I can't see any way to work around this
>> limitation. Not having to worry about variable-length structures
>> simplifies semantic analysis and other clients (CodeGen being the big
>> one).
> 
> How hard would it be for us to actually support this extension in Sema?
> 
> I haven't looked or thought about it, but it doesn't seem all that
> different from the things we already do for variable length arrays.
> 
> If Sema support is do-able and not too horrible, then we could provide
> the feature but disable it when using a compiler. This would at least
> allow clients other than the compiler to parse, analyze, etc. the
> code.

This is exactly what I hope and it's perfect for our needs. Although
CodeGen will not support this extension, to have a complete AST is very
important for other kind of clients.