Re: gcc visibility used by moz

[Jason Merrill <jason at redhat dot com>]

Gabriel Dos Reis wrote:
>> Joe Buck wrote:
> Now, this being a conscious decision for ODR violation, it would
> probably need to be documented because then we may have
>
>    typeinfo1 != typeinfo2
>
> and yet
>
>     !typeinfo1.before(typeinfo2) && !typeinfo2.before(typeinfo1)
>
> There are probably other inconsistencies to audit.
>
> | We can have two distinct
> | classes named S, and no one can tell.  Each bit of code will see one
> | definition of S.

I think that Joe's point is that IF you have two classes named S, then 
they're hidden away in separate shared libraries and you can't compare 
them, because no piece of code knows about both of them.  Any class that 
is part of the public interface of a shared library is part of the 
public interface, and therefore must be unique through the program.

In any case, this ODR business seems rather tangential to the discussion 
of visibility semantics.  The primary purpose of the visibility work is 
limiting the number of symbols exported from a particular shared library 
in order to cut down on load time.  Can we please focus on the semantics 
we want for that instead of trying to solve a theoretical problem that 
has been around as long as people have tried to use shared libraries 
with C++?

Jason