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Date: Thu, 21 May 2015 23:23:35 -0700 (PDT)
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Subject: GNAT bugs around use of "for X'Address..." clause
From: erik.shadwick@gmail.com
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Xref: news.eternal-september.org comp.lang.ada:25934
Date: 2015-05-21T23:23:35-07:00
List-Id: <comp.lang.ada>

Consider the following declarations:

package P is
   type Checked_T is private
     with Type_Invariant =3D> Check (Checked_T);

   type Tagged_T is tagged private;

   type Checked_Tagged_T is tagged private
     with Type_Invariant =3D> Check (Checked_Tagged_T);

     function Check (M : Checked_T)        return Boolean with Inline;
     function Check (M : Checked_Tagged_T) return Boolean with Inline;

private
   type Checked_T is null record;
   type Tagged_T is tagged null record;
   type Checked_Tagged_T is tagged null record;

   function Check (M : Checked_T) return Boolean is (True);
   function Check (M : Checked_Tagged_T) return Boolean is (True);

end P;


Then the following 3 declarations each produce [similar] GNAT BUG DETECTED =
output:

X : P.Checked_T;
for X'Address use System.Null_Address;
--  However, if I do something like:
--     V : P.Checked_T;
--     X : P.Checked_T :=3D V;
--     for X'Address use ...;
--  then no bug surfaces.

W : P.Tagged_T;
Y : P.Tagged_T :=3D W;
for Y'Address use System.Null_Address;
--  If I do not perform the ":=3D W", then it works fine.
   =20
Z : P.Checked_Tagged_T;
for Z'Address use System.Null_Address;
--  With or without assignment to Z in its declaration, it fails.


(Compiled with `gnatmake -gnat2012`, with "GPL 2014 (20140331) (x86_64-appl=
e-darwin12.5.0)")

Should I be submitting this to AdaCore, or GCC's http://gcc.gnu.org/bugs.ht=
ml bug tracker? When running this with my copy of GNAT free/GPL, it suggest=
s the former, but when compiling it through ideone.com I get the message to=
 put it into GCC's tracker. It detects the error in "in gnat_to_gnu_entity,=
 at ada/gcc-interface/decl.c:347".

Further, what is the validity of assigning to a variable that has the 'Addr=
ess clause on it -- is it legal and defined behaviour?

--
Erik Shadwick