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From: bourguet@my-deja.com
Subject: Are unconstrained arrays passed by references?
Date: 1999/08/10
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Date: 1999-08-10T00:00:00+00:00
List-Id: <comp.lang.ada>

In the Intermetric X bindings, there is something like this in
X.Strings (this is from memory, I may mess up the details but
the principle should be clear):

subtype char is Interfaces.C.char;
type charp is access all char;

function Addr (S : String) return charp;

function To_X (A : System.Address) return charp is
   new Unchecked_Conversion...

function Addr (S : String) return charp is
begin
   return To_X (S (S'First)'Address);
end Addr;

There is a warning to use Addr only with variables and constants
because if the argument was an expression the result may be
dangling before it was of any use.

I understand how this work if the string is passed by reference,
and why passing unconstrained array by reference make sense,
but as I've not found in the RM indications that it is mandatory
I was wondering if I've missed something or if this code rely on
a probable implementation.

Thanks.

-- Jean-Marc


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