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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Uninitialized out parameters.
Date: Wed, 6 Apr 2016 16:01:46 -0500
Organization: JSA Research & Innovation
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Xref: news.eternal-september.org comp.lang.ada:30021
Date: 2016-04-06T16:01:46-05:00
List-Id: <comp.lang.ada>

I said:
> It *seems* like checks like the one Ahlan is suggesting are a good idea, 
> until you trip over one. (The check in Ada that every function have at 
> least one return is a similar idea, which causes no end of trouble.)

On top of that, exactly what would the check be? Which of the following 
ought to be illegal?

      procedure Foo1 (Obj : out Positive) is null;

      procedure Foo2 (Obj : out Positive) is
      begin
           null;
      end Foo2;

      Debug : constant Boolean := False;
      procedure Foo3 (Obj : out Positive) is
      begin
            if Debug then
                 Put_Line ("Foo3 called");
            end if;
      end Foo3;

Foo1 and Foo2 are semantically identical (Foo1 is in fact defined in terms 
of Foo2). But it is clearly a lot harder for an Ada compiler to detect Foo2 
compared to Foo1 (and changing between them is common). Having different 
legality for Foo1 and Foo2 would be annoying at best.

Obviously, detecting Foo3 is even harder for a compiler, but again, 
semantically it is identical to Foo2. So where do you stop? And why?

                                          Randy.