Re: using 'address to make indrect calls

["Raymond C. Rawa" <Raymond.C.Rawa@nospam.boeing.com>]

Pascal MALAISE wrote:

> The instanciation in make within a procedure/function.
> The validity of the instanciated objects ends when the procedure ends.
> Suppose G_PKG declares objects (variables, procedures) and test stores
> the address of such object in a "global", remanent variable (in a
> package spec):
> other_package.g_object_address := g.object'address
> the using other_package.g_object_address after the end of g leeds to
> unpredicable result.
> The compiler does not know that test is your main procedure. Neither do
> I,
> but I suppose, and in this case (test is the "main") there is no danger.
> 
> If you want to get rid of the warning:
> with G_PKG;
> package g is new G_PKG;
> 
> with g;
> procedure test is
> 
> Then the instanciation is more "static".

Thank you, for your help.  Your solution worked like a charm for the
test case.

Alas, the test case I proposed is too simplistic.  In my actual
application, the generic package is instantiated within a package body,
not a procedure.


Here's what I'm really trying to do...  

(1) I've got a task out there that receives procedure addresses and
attempts to execute them in it's thread of control.
(2) I've got a bunch of packages out there that send callback procedure
addresses to the task.


The first two seem to work just fine, here's the complication...

(3) Some packages need to pass a parameter to the callback routines. 
The task only handles parameterless procedures.
(4) So I've created a generic package that can be instanciated with the
desired parameter type.  It contains two procedures.

procedure Call_Procedure_With_Parameter(
   Procedure_Address : SYSTEM.Address;
   Parameter         : Parameter_Type;
-- places Procedure_Address  and Parameter into a queue.
-- passes Call_Queued_Procedure'address to the above mentioned task.

procedure Call_Queued_Procedure;
-- pop's an address and parameter off the queue
-- executes the procedure located at Procedure_Address with Parameter

(5) Now any package that needs to pass parameters to it's callback
routine can simply instanciate my generic with the desired type and
execute the Call_Procedure_With_Parameter routine.

My problem seems to be that the compiler doesn't know that the procedure
address specified in the generic package is valid, so it produces a
warning message.

I guess as long as I instanciate the generic package at either the
library level or within a package or procedure that is elaborated at the
library level I'm fine.  I just wish I could supress that darn warning.



Raymond C. Rawa
V-22 Operational Software IPT
Digital Map Software Designer
Raymond.C.Rawa@Boeing.com

Oh by the way, I'm stuck in Ada83