Re: Dispatching callback handed over to C

[Maciej Sobczak <see.my.homepage@gmail.com>]

On 3 Kwi, 14:02, Natasha Kerensikova <lithium...@gmail.com> wrote:

> But still, I can't help but think there is one needless subprogram call
> in that solution. With a way to obtain the address of the actual
> subprogram the dispatching call would dispatch to, the address could be
> handed over to C code so that it can call it directly.

Then the target operation would need to have a C calling convention.
Since one of the reasons to do OO is to allow users to extend the
system with new operations (new implementations), this requirement
would be a limitation.
The indirection allows to completely isolate the user from such
details.

> Actually it uses the assumption that System.Address and void* have the
> same representation.
>
> I wonder how reliable the assumption is.

Whenever Ada and C (or C++) components are linked together, a set of
"friendly" compilers is needed, so that basic binary compatibility can
be guaranted - otherwise nothing is going to work at all, not even
Interfaces.C.int. :-)
This assumption is pretty safe.

--
Maciej Sobczak * http://www.inspirel.com