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Newsgroups: comp.lang.ada
Subject: Re: Help: program won't ends (GNAT)
From: Georg Bauhaus <bauhaus@arcor.de>
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Date: Mon, 22 Jan 2007 11:54:22 +0100
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Date: 2007-01-22T11:53:29+01:00
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On Mon, 2007-01-22 at 10:14 +0200, Niklas Holsti wrote:
> Yves Bailly wrote:

> > When I run the program, both strings are displayed, but the program doesn't
> > exit: it just keeps running, eating 75% of my CPU power
>   ...
> I observe the same behaviour on gnat 3.15p, Debian Linux. Seems to be a 
> GNAT bug of respectable age.
> 

It seems there is a circle in the pointers used
for unbounded string in this case.
Finalization jumps back and forth between

 Ada.Strings.Unbounded.Finalize  (Object : in out Unbounded_String) 
and
 System.Finalization_Implementation.Finalize_List (L : Finalizable_Ptr)

where object.reference = Null_String'Access
  and object.next = L -- same address!?

But Ada.Strings.Unbounded.Finalize does nothing, probably because:
--  Note: Don't try to free statically allocated null string

There is a loop in Finalize_List which intending to step
along the list in L and call Finalize on each pointer.
But this pointer stays the same.

Can any GNAT expert have a look, please?