[cfe-dev] Unneeded declarations invalidation

Daniel Dunbar daniel at zuster.org
Fri Jul 24 16:37:36 PDT 2009

On Tue, Jul 21, 2009 at 2:34 PM, Eli Friedman<eli.friedman at gmail.com> wrote:
> On Tue, Jul 21, 2009 at 1:11 PM, Daniel Dunbar<daniel at zuster.org> wrote:
>> How hard would it be for us to actually support this extension in Sema?
> Hmm... to support it properly, we'd have to add flags to structures to
> note that they're variable length or variably modified, make sure to
> mark structs and arrays containing such structs as variable
> length/variably modified as appropriate, avoid trying to compute
> anything that requires the layout for such structures in Evaluate,
> adjust isICE to perform checks as appropriate, disallow initializers
> for such structures, adjust isVariablyModifiedType, disallow
> variable-size structs with static storage duration, disallow
> redeclaring a tag with a variably modified type, disallow
> variable-size structs in function parameters/return values, adjust
> various places in ObjC code to disallow them, and adjust the goto
> verifier to look for RecordDecls.  There's probably some stuff I'm
> forgetting, but that's everything I can think of off the top of my
> head.

Nice list! :)

It's certainly a non-trivial amount of work, but I don't think any of
those things make Sema particular gross. I'm not personally motivated
to add it, for example, but if someone was willing to contribute work
towards it I think we would accept it?

 - Daniel

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