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From: Ullar Kask <ullar@einstein.ph.utexas.edu>
Subject: Aggregate assignment problem with gnat under irix
Date: 1996/05/31
Message-ID: 
 <Pine.SGI.3.93.960531171236.29298A-100000@einstein.ph.utexas.edu>#1/1
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organization: The University of Texas at Austin, Austin, Texas
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reply-to: ullar@einstein.ph.utexas.edu
newsgroups: comp.lang.ada
Date: 1996-05-31T00:00:00+00:00
List-Id: <comp.lang.ada>


Hello,

  I am doing numerical simulations using Ada and encoutered a problem with
aggregate assignment. The same type of statement, viz.,

  A.all := (others => (others => 0.0));

where A.all is an NxN array (declared as unconstrained), works great in simple
procedures but fails in a task body. I don't understand what may be
the reason.

To be more specific, consider the following piece of code (compiles cleanly
with irix5.3 binary distribution of gnat 3.04 under irix5.2):

--------------------------------------------------------------------------------

with Ada.Text_IO, Interfaces.Fortran, Ada.Exceptions;
use  Ada.Text_IO;

procedure Aggr_Tst is

  subtype Real is Interfaces.Fortran.Real;

  type Matrix_Type is array (Integer range <>, Integer range <>) of Real;
  pragma Convention( Fortran, Matrix_Type);

  type Matrix_Type_Access is access Matrix_Type;

  type Grid_Type is (COARSE, MEDIUM, FINE);


  Lhs : array (Grid_Type) of Matrix_Type_Access;


  Grid_Length : array (Grid_Type) of Positive;

  Grid        : Grid_Type;


  task Some_Task is
    entry Entry_Point( G : in Grid_Type);
  end Some_Task;


  task body Some_Task is

    Grid : Grid_Type;

  begin

    accept Entry_Point( G : in Grid_Type) do
      Grid := G;
    end Entry_Point;

    --
    -- Some work is being done here with Lhs(Grid).all
    -- After that, try to initialize it again:
    begin

      -- The following statement raises STORAGE_ERROR:
      Lhs(Grid).all := (others => (others => 0.0));

      -- So does this:
--      Lhs(Grid).all := (Lhs(Grid).all'RANGE(1) =>
--                        (Lhs(Grid).all'RANGE(2) => 0.0));

      -- And this:
--      Lhs(Grid).all := (-Grid_Length(Grid) .. Grid_Length(Grid) =>
--                        (-Grid_Length(Grid) .. Grid_Length(Grid) => 0.0));

      -- Only the following double-loop does the job:
--      for I in Lhs(Grid).all'RANGE(1) loop
--        for J in Lhs(Grid).all'RANGE(2) loop
--          Lhs(Grid)(I,J) := 0.0;
--        end loop;
--      end loop;

    exception
      when O: others =>
        Put_Line( "***Lhs initialization failed!***  Exception " &
                  Ada.Exceptions.Exception_Name(O) & " raised in task body.");
        raise;
    end;

    Put_Line( "Lhs initialized again in task body.");

  end Some_Task;


begin

  -- Some values assigned to Grid and Grid_Length(Grid):
  Grid := COARSE;
  Grid_Length(Grid) := 100;

  -- Allocate matrix:
  Lhs(Grid) := new Matrix_Type(-Grid_Length(Grid) .. Grid_Length(Grid),
                               -Grid_Length(Grid) .. Grid_Length(Grid));

  -- Initialize matrix:
  begin

    Lhs(Grid).all := (others => (others => 0.0));   -- This works fine

  exception                                         -- No exceptions raised here
    when Q: others =>
      Put_Line( "***Lhs initialization failed!***  Exception " &
                Ada.Exceptions.Exception_Name(Q) & " raised in main procedure");
      raise;
  end;

  Put_Line( "Lhs initialized in main procedure.");


  -- Do some work with the matrix:
  Some_Task.Entry_Point( Grid);

end Aggr_Tst;
------------------------------END OF CODE SAMPLE--------------------------------


Has the STORAGE_ERROR raised in the task body (under irix) something to do
with the size of the task stack? How it happens that such an aggregate
assignment is possible outside a task body but fails inside?

Any comments on the issue are appreciated!

Thanks a lot!


================================================================================
�llar Kask
Center for Relativity, University of Texas, Austin
email: ullar@einstein.ph.utexas.edu
ph. (512) 471-5905
http://wwwrel.ph.utexas.edu/Members/ullar/