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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Error in gnat-4.6  (opensuse 11.4) ?
Date: Thu, 17 Mar 2011 14:34:29 +0000
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reinkor <reinkor@gmail.com> writes:

> raised STORAGE_ERROR : stack overflow (or erroneous memory access)
>
> If I change:   "type Real is Digits 16;"  ->  "type Real is Digits
> 15;"
> then I do not get "stack overflow".  Similarly, if I comment out for
> example the statement " fe,xe : fe_t;"

>    type Real is Digits 16;

This (on Intel hardware) asks for what GNAT calls Long_Long_Float, which
requires 10 bytes. "digits 15" asks for Long_Float, which requires 8
bytes.

>    type f_t  is array(1..0400) of Real;
>    type fe_t is array(1..1000) of Real;
>
>    type Node_t is
>      record
>         f, fm : f_t;
>         fe,xe : fe_t;
>         x  : Real;
>      end record;
>
>    Node : array (1..200) of Node_t;

Node is declared on the stack, and uses 200*(400+400+1000+1000+1) =
560_000 Reals, which for Long_Float uses under 5MB of stack, for
Long_Long_Float uses just over and is probably the cause of your
reported stack_overflow.

You might be able to improve matters by using the ulimit command; it
didn't work here (Mac OS X). The only real way is to use heap
allocation:

   type Node_Array is array (Positive range <>) of Node_t;
   type Node_Array_P is access Node_Array;

   Node : Node_Array_P := new Node_Array (1..200);