Re: gcc visibility used by moz

[Andrew Pinski <pinskia at physics dot uc dot edu>]

On Jul 12, 2006, at 10:04 AM, Tristan Wibberley wrote:
> This isn't "type" visibility. Shared objects don't export "types"  
> they export "symbols". The types are defined in headers and are  
> thus known to exist - no visibility attributes will or should  
> change that.

Actually in C++, they are exported, it is one of the "funny" things  
which people don't realize about
C++.  This is the normal ODR (one definition rule) rules which are  
coming into play which
the visibility on the class, it is not no longer exported from the  
shared library.

> If the programmer had intended that the type should appear to not  
> exist. it wouldn't be defined in a header #include-able by client  
> code. The compiler should assume that the type exists and can be  
> used if it is defined and shouldn't change attributes on other  
> parts of the program.

But that code would be invalid (though no diagnostic is required)  
code by the ODR rules in C++.

This is the main difference between C++ and C where in C compatible  
types actually can have different
names while in C++ they cannot and if two different types in C++ are  
the same name, the code is invalid
(though no diagnostic is required).

-- Pinski