Re: GNAT's stack checking in Ubuntu 9.04 (and Shootout regex-dna)

[Brian Drummond <brian_drummond@btconnect.com>]

On Tue, 04 Aug 2009 00:54:11 +0200, Georg Bauhaus
<rm.tsoh.plus-bug.bauhaus@maps.futureapps.de> wrote:

>The GNAT that comes with Ubuntu 9.04 (GCC 4.3.3)
>produces storage errors where GNAT on Debian Lenny
>(GCC 4.3.2) and GNAT 2007 on Windows (4.3.1) don't.
>This happens with larger data structures.
>
>The workaround is to introduce an indirection ... (.-)

Default stack sizes may change between GCC versions and I've had trouble getting
the stack size flags to work on some versions. 

I've done this too. What I don't like is having to change every use of the
indirect variable, so I confine the changes to the declaration...

>--- regexdna.gnat       6d8829eff6a278659ecb6ebc0f03672662de39b8
>+++ regexdna.gnat       09cbee8b34b6bc62a921d8bfc66e2f18cb57eeb6
>@@ -120,7 +120,8 @@ begin
>       Num_Lines := Num_Lines + 1;
>    end if;
>    declare
>-      Sequence_Lines : Dna_Lines(1..Num_Lines);
>+      type Dna_Lines_Pointer is access Dna_Lines;  -- avoids stack issues
>+     -- Sequence_Lines : Dna_Lines_Pointer := new Dna_Lines(1..Num_Lines);
       Sequence_Lines_ptr : Dna_Lines_Pointer := new Dna_Lines(1..Num_Lines);
       Sequence_Lines : Dna_Lines(1..Num_Lines) renames Sequence_Lines_ptr.all;

and now no changes are necessary to the program (which may access the variable
many times)

>      Put(Item => Length(Sequence_Lines), Width => 1);

- Brian