Re: Elaboration order

[ncohen@watson.ibm.com (Norman H. Cohen)]

In article <4io8rn$gfn@newsbf02.news.aol.com>, denreimer@aol.com (DenReimer)
writes: 

|> Here's something that I'm trying to do in Ada83 and Ada95: 
|>
|> with GENERIC_PACKAGE;
|> package A_PKG is
|>    package INSTANCE is new GENERIC_PACKAGE ( ... );
|>    X : INTEGER := INSTANCE.SOME_FUNCTION;
|> end A_PKG;
|>
|> The elaboration of X requires that the instantiated package INSTANCE be
|> elaborated first (both spec and body.)  The compiler will not let me use
|> pragma elaborate (INSTANCE);
|>
|> It is not clear to me what the elaboration order should be in the case of
|> nested packages.  I would like to assume that for nested packages, the
|> elaboration is also nested.  In the case of generic instantiations, both
|> spec and body would be elaborated at the point of instantiation.
|> Unfortunately, the LRM does not seem to make any requirements regarding
|> elaboration order for nested packages.

RM83-7.2(3), RM95-7.1(8): "The elaboration of a package declaration
consists of the elaboration of its basic declarative items in the given
order."

RM83-12.3(17): "For the elaboration of a generic instantiation, ....
Finally, the implicitly generated instance is elaborated."
RM95-12.3(20) is more explicit: "Finally, the instance declaration and
body are elaborated."

Thus both the declaration and body of Instance are sure to be elaborated
before the declaration of X is elaborated.

|> When I use gnat, I get a program error.

Possibly from an attempt to instantiate the TEMPLATE before its GENERIC
BODY has been elaborated.  (See RM83-3.9(7), RM95-3.11(13).)
Change your context clause to: 

   with Generic_Package; pragma Elaborate(Generic_Package);

--
Norman H. Cohen    ncohen@watson.ibm.com