Re: win32ada design question/problem

[tmoran@bix.com]

>   C_Function(S'Address);
>
>makes it clear that you are passing the whole of S.
> ....
>   C_Function(S(S'first)'Unchecked_Access);
>
>which does not make clear that S is passed as a whole.
   C_Function(Window_Name => S(S'first)'Unchecked_Access);
or
   C_Function(Control_Character => S(S'first)'Unchecked_Access);
Using a named parameter should make it clearer in either case.
A maintainer familiar with C would realize that all of S is
potentially accessible by S(S'first)'Unchecked_Access and would
have to look up C_Function to find out if it's acting on just
(S'first) or other parts of S.  Ditto S'Address.
(And of course S probably is intended to be an Interfaces.C.Char_Array,
not an Ada String.)

>- Try interfacing fcntl, setsockopt or some other weird functions using
>access types: these somtimes return, or take as a parameter, a pointer
>that points to a type that changes depending on the function you want to
>perform, which is determined by the value of another parameter. You can
>certainly do this with overloading, but I am not sure this buys much in
>a thin binding.
  This certainly happens, but relatively rarely.  I take it as yet
another argument against too-thin bindings.

>- It's the good old Ada 83 way that has worked for 15 years now, wo why
>change ?
  Actually, no. My first Ada 83 compiler used fat pointers for
unconstrained arrays and S'Address would not do what you expected in that
case - it was necessary to use S(S'first)'Address.
Tom Moran