Export and Protected Scoping in Dynamic Libraries

[Jacob Carlborg]

On 2011-12-16 10:34, Walter Bright wrote:
> On 12/14/2011 11:41 AM, Adam Wilson wrote:
>> Hello Everyone,
>>
>> I want to start this conversation by pointing out that I come from a
>> C/C++/C#
>> background and my ideas and frustrations in this post will be colored
>> by that
>> history.
>>
>> When I first approached D, the idea of an 'export' confused me. I've
>> since
>> figured out, at least in libraries, that in C# terms D's 'export' means
>> 'public'.
>
> I'm not too familiar with C#'s public, but what D 'export' means is a
> function is an entry point for a DLL. In the Windows world, that means
> it gets an extra level of indirection when calling it, and it
> corresponds to:
>
> __declspec(export)
>
> in Windows compilers.
>
>> However, this raise a problem, specifically, how do I export a
>> protected member from a dynamic library?
>
> Do you mean how does one directly call a protected function inside a DLL
> from outside that DLL, without going through the virtual table?

What I think he wants is a member that is overrideable in a subclass 
outside of the DLL but otherwise only reachable within the module its 
defined in.

// foo.dll/foo.d
class Foo
{
     export protected void foo () {}
}

// foo.dll/bar.d
auto foo = new Foo;
foo.foo; // error can't access protected member

// bar.dll/bar.d
class Bar : Foo
{
     export protected override void foo () {} // it's fine to override 
the method since it's protected, it's reachable in this dll since it's 
exported
}

-- 
/Jacob Carlborg