Re: A bug in Gnat, or in my code?

[Preben Randhol <randhol+abuse@pvv.org>]

In comp.lang.ada, you wrote:
> Preben Randhol wrote:
>
>> That said what are you trying to do with the code? It looks wierd
>> to me.
>
> Of course that code is useless. That's just a stripped test case. The 
> bug occurs in To_Unbounded_String, called from this procedure:
>
>        procedure klyv(argument : in string;
>                       namn : out unbounded_string;
>                       text : out unbounded_string) is
>           use Ada.Strings;
>           use ada.strings.fixed;
>           pos : natural;
>        begin
>           pos := index(argument, "=");
>           if pos = 0 then
>              pos := argument'last + 1;
>           end if;
>           namn := to_unbounded_string(
>                      trim(argument(argument'first .. pos - 1), both));
>           text := to_unbounded_string(
>                      argument(pos + 1 .. argument'last));
>        end klyv;
>
> It splits a string of the format "name=value" into two. If there is no 
> equal sign, the whole string goes into Namn, and Text should become an 
> empty string. In that case To_Unbounded_String is called with 
> Argument(Argument'Last+2..Argument'Last), which triggers the bug.

I see. I think you have a bug in that you forgot to trim the text.
Anyhow I made a test of your program and ran it on gnat 3.3.3 from
Debian and it works there. No crash. So maybe it is only the packaging
of RedHat? A program shouldn't segmentation fault and this is typically
an indication of a packaging/installation error.


   % gnatmake -f -gnatv klyv_test.adb 
   gcc-3.3 -c -gnatv klyv_test.adb

   GNAT 3.3.3 (Debian)
   Copyright 1992-2002 Free Software Foundation, Inc.

   Compiling: klyv_test.adb (source file time stamp: 2004-03-11 14:46:48)
    46 lines: No errors
   gnatbind -x klyv_test.ali
   gnatlink klyv_test.ali

   % ./klyv_test 
   Ada 95 = morsomt => Ada 95&morsomt
   Ada 95 morsomt => Ada 95 morsomt&

Here is my program:

klyv_test.adb
-------------------------------------
with Ada.Text_IO; use Ada.Text_IO;
with Ada.Strings;
with Ada.Strings.Fixed;
with Ada.Strings.Unbounded;  use Ada.Strings.Unbounded; 

procedure klyv_test is

   procedure klyv(argument : in string;
                  namn : out unbounded_string;
                  text : out unbounded_string) is
      use Ada.Strings;
      use ada.strings.fixed;
      pos : natural;
   begin
      pos := index(argument, "=");
      if pos = 0 then
         pos := argument'last + 1;
      end if;
      namn := to_unbounded_string(
                 trim(argument(argument'first .. pos - 1), both));
      text := to_unbounded_string(
                 trim(argument(pos + 1 .. argument'last), both));
   end klyv;

   Hoggestabbe1 : constant String := "Ada 95 = morsomt";
   Hoggestabbe2 : constant String := "Ada 95 morsomt";
   Tekst_foer : Unbounded_String;
   Tekst_etter : Unbounded_String;
begin

   klyv (Hoggestabbe1, Tekst_foer, Tekst_etter);

   Put_Line (Hoggestabbe1 & " => " & 
             To_String (Tekst_foer) & "&" &
             To_String (Tekst_etter));

   klyv (Hoggestabbe2, Tekst_foer, Tekst_etter);

   Put_Line (Hoggestabbe2 & " => " & 
             To_String (Tekst_foer) & "&" &
             To_String (Tekst_etter));


end klyv_test;
-------------------------------------

Preben
-- 
Preben Randhol -------------- http://www.pvv.org/~randhol/Ada95 --
                 �For me, Ada95 puts back the joy in programming.�