[Bug c/71255] Implement #pragma may_alias

[rguenther at suse dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71255

--- Comment #11 from rguenther at suse dot de <rguenther at suse dot de> ---
On Tue, 24 May 2016, mpolacek at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71255
> 
> --- Comment #10 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
> Well, so far my plan is to gather symbols in
> #pragma GCC may_alias SYMBOL
> to some vector of symbols and then when declaring a SYMBOL check if it's in the
> vector and if so, apply the may_alias attribute.  Now, as Richi points out,
> I'll probably have to introduce two variants:
> 
> #pragma GCC may_alias SYMBOL
> #pragma GCC may_alias struct SYMBOL
> 
> The symbols in the vector would serve as a "tentative" forward declaration.
> 
> Do you see any problems with that?

Not really but a

#pragma GCC tentative
struct sockaddr __attribute__((may_alias));

would then also allow for other attributes to be tentatively added so
that might be a little less special.