Re: pragma Convention questions

[Martin Krischik <krischik@users.sourceforge.net>]

Samuel Tardieu wrote:

> I have several questions regarding pragma Convention in Ada95 for
> language lawyers.

The language lawyers are on mailto: ada-comment@ada-auth.org ;-)
 
> 1- pragma Convention on private types in language-define packages
> 
> Is it allowed for a compiler implementor to use a pragma Convention
> on a private type in a language-defined package?
> 
> For example, would it be allowed to use
> 
>   pragma Convention (C, chars_ptr);

Yes. However the type must not be used beforehand - which is unlikely. Real
language lawyers can tell you the term after which a type can not have any
further modifications.
 
> in the private part of Interfaces.C.Strings? (the real motive to this
> question is to get rid of a warning in GNAT about conversion between
> pointers of different conventions -- the type is already compatible
> with C as per RM B3.1(1))
> 
> 2- pragma Convention, renaming and Intrinsic
> 
> Is the following code legal?
> 
> package U is
>    type Foo is (Foo1, Foo2);
>    function F return Foo renames Foo1;
>    pragma Convention (Ada, F);
>    type Foo_Access is access function return Foo;
>    X : Foo_Access := F'Access;
> end U;
> 
> GNAT rejects X initialization with 'prefix of "Access" attribute
> cannot be intrinsic'. Which means that the pragma Convention failed
> silently. Is it allowed to have it fail without a compilation error?
> Or is the 'Access legal?

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

pragma Export (Ada, F);

But somehow I think that will fail because F does exists physically. Same
way you can do: 

enum Foo {Foo1, Foo2};
#define F Foo1
Foo *X = &F;

in C. (I take it you know C).

Martin

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