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From: anon@anon.org
Newsgroups: comp.lang.ada
Subject: Re: Warnings about hiding
Date: Sat, 9 Oct 2010 11:18:37 +0000 (UTC)
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Date: 2010-10-09T11:18:37+00:00
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In <44e7dff1-04f5-46ad-8521-e4fe030c9c29@26g2000yqv.googlegroups.com>, Julian Leyh <julian@vgai.de> writes:
>Hi,
>
>"-gnatwh" activates warnings on hiding declarations. But sometimes,
>hiding is necessary.
>
>For example, consider this (Controlled type with it's own comparison
>operator and finalize procedure, you can reproduce the errors using
>these ads files):
>
>$ cat foo.ads
>with Ada.Finalization;
>package foo is
>   type Foobar is new Ada.Finalization.Controlled with null record;
>   function "=" (L,R : in Foobar) return Boolean;
>private
>   procedure Finalize (Object : in out Foobar);
>end foo;
>$ gnat -gnatwh -gnatc foo.ads
>gcc -c -gnatwh -gnatc foo.ads
>foo.ads:4:13: warning: declaration of "=" hides one in package
>Standard
>foo.ads:6:14: warning: declaration of "Finalize" hides one at line 3
>$
>
>The only way i see to solve this, is using pragma Warnings (Off); like
>this:
>
>$ cat bar.ads
>with Ada.Finalization;
>package bar is
>   type Barfoo is new Ada.Finalization.Controlled with null record;
>pragma Warnings(Off);
>   function "=" (L,R : in Barfoo) return Boolean;
>pragma Warnings(On);
>private
>   procedure Finalize (Object : in out Barfoo);
>end bar;
>$ gnatmake -gnatc -gnatwh bar.ads
>gcc -c -gnatwh -gnatc bar.ads
>bar.ads:8:14: warning: declaration of "Finalize" hides one at line 3
>$
>
>But that would either remove all warnings between both pragmas, or I
>would have to put them around every occurence of the hiding. I don't
>like turning all warnings off at once and I don't like adding two
>lines of source code just to prevent the warning. Still, I would like
>to remove them (without removing -gnatwh).
>
>Is there a proper way to do this?
>
>Greetings,
>Julian

RM 8.3 (19) defines your problem.  In your example there is no fix.  Your 
just trying to violate Ada's visibility rules is all.

Plus, the "-gnatwh" just states which routines or variables that are hidden by 
redefinition or overloading routines and variables.

So, drop the requirement of using "-gnatwh" is the only answer.  Unless you 
want or need to see what caused the first routine or variable to be hidden.


To see a better example of this. Copy s-fileio.ad? (System.File_io.ad?) to a 
test directory and compile using "-gnatwh".  I chose s-fileio.ad? because it 
has and similar code as your example.  In compiling you will get all kinds 
of warning messages about like 
  "declaration hides "SSL" at a-except.ads"
or 
  "declaration of "Finalize" hides one at line"