Re: pragma Convention questions

[Samuel Tardieu <sam@rfc1149.net>]

>>>>> "Martin" == Martin Krischik <krischik@users.sourceforge.net> writes:

Martin> Yes. However the type must not be used beforehand - which is
Martin> unlikely. Real language lawyers can tell you the term after
Martin> which a type can not have any further modifications.

Thank you, I know the freezing rules and they would not be
violated. My question was related to the legality of doing that when
I could not find the RM section which allows you to change the default
convention (Ada) of language-defined types (Interfaces.C.Strings.chars_ptr).

Martin> F does not actually exist and therefore has no address to
Martin> access. And for "Convention Ada" that's ok. What you really
Martin> meant to do is:

Martin> pragma Export (Ada, F);

I don't think so, pragma Convention should be enough. Note that
renaming an existing function instead of an enumeration literal
doesn't exhibit the same behaviour.

Martin> But somehow I think that will fail because F does exists
Martin> physically.

It doesn't exist physically because it inherits the convention of the
renamed entity (the enumeration literal, which has an Intrinsic
convention). That's precisely why I don't understand why GNAT lets me
specify its convention if it isn't able to honor it.

Note that the fact that an enumeration literal doesn't exist
physically as a function doesn't prevent you from using it as a
generic actual subprogram:

package W is
   generic
      with function F return Boolean;
   package Gen is end Gen;
   package Inst is new Gen (False);
end W;

(however, legality rules prevent you from ever taking a 'Access from
inside the generic as formal subprograms are not subtype conformant
with anything else, so my question would be void in this case)

The more I think about it the more I think GNAT should refuse the
pragma Convention, just as it refuses it if you try to apply it
directly to an enumeration literal. That's why I'd like some advice
here. I'll ask ada-comment, I hadn't thought about it, thanks.

Martin> I take it you know C

Yup, but there is no need to resort to an inferior language :)

  Sam
-- 
Samuel Tardieu -- sam@rfc1149.net -- http://www.rfc1149.net/