[Bug ada/42140] GNAT appears to misbehave with limited tagged types and possibly finalization

["john at johnnowak dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #3 from john at johnnowak dot com  2009-11-22 17:02 -------
Subject: Re:  GNAT appears to misbehave with limited tagged types and possibly
finalization

You know, your code would be a lot better if you didn't use anonymous  
access types. (:-))

On Nov 22, 2009, at 11:41 AM, gcc at coreland dot ath dot cx wrote:

>
>
> ------- Comment #2 from gcc at coreland dot ath dot cx  2009-11-22  
> 16:41 -------
> A couple of people have commented on the anonymous access type
> (claiming it causes the crash). Here's a version with it removed
> and a gdb backtrace:
>
> Program received signal SIGSEGV, Segmentation fault.
> system.finalization_implementation.move_final_list  
> (from=0x800a02040, to=0x0)
> at s-finimp.adb:486
> 486     s-finimp.adb: No such file or directory.
>        in s-finimp.adb
> (gdb) bt
> #0  system.finalization_implementation.move_final_list  
> (from=0x800a02040,
> to=0x0) at s-finimp.adb:486
> #1  0x0000000000402cfb in archiver.open_archive (archiver=(),  
> path=0x41fe18,
> <open_archiveBIPalloc>=4324888,
>    <open_archiveBIPfinallist>=0x0,  
> <open_archiveBIPaccess>=0x7fffffffe6d8) at
> archiver.adb:9
> #2  0x0000000000402e9f in main () at main.adb:9
>
> Probably advisable to add an assertion in Move_Final_List
> to ensure that 'To' is not null.
>
> -- %< archiver.ads
>
> with Ada.Finalization;
> with Ada.Streams.Stream_IO;
>
> package Archiver is
>
>  type Archiver_t is tagged limited private;
>  type Archive_t  is tagged limited private;
>
>  function Open_Archive
>    (Archiver : in Archiver_t;
>     Path     : in String) return Archive_t'Class;
>
>  function Stream
>    (Archive : in Archive_t)
>      return Ada.Streams.Stream_IO.Stream_Access;
>
> private
>  package Stream_IO renames Ada.Streams.Stream_IO;
>
>  type Archiver_t is tagged limited null record;
>
>  type Archive_t is new Ada.Finalization.Limited_Controlled with record
>    File : Stream_IO.File_Type;
>  end record;
>
> end Archiver;
>
> -- %< archiver.adb
>
> package body Archiver is
>
>  function Open_Archive
>    (Archiver : in Archiver_t;
>     Path     : in String) return Archive_t'Class
>  is
>    pragma Unreferenced (Archiver);
>  begin
>    return A : Archive_t'Class :=
> Archive_t'(Ada.Finalization.Limited_Controlled with others => <>) do
>      Stream_IO.Open
>        (Name => Path,
>         File => A.File,
>         Mode => Stream_IO.In_File);
>    end return;
>  end Open_Archive;
>
>  function Stream
>    (Archive : in Archive_t)
>      return Ada.Streams.Stream_IO.Stream_Access is
>  begin
>    return Stream_IO.Stream (Archive.File);
>  end Stream;
>
> end Archiver;
>
> -- %< main.adb
>
> with Ada.Text_IO;
> with Ada.Streams.Stream_IO;
> with Archiver;
>
> procedure Main is
>
>  A : Archiver.Archiver_t;
>  S : constant Ada.Streams.Stream_IO.Stream_Access := Archiver.Stream
> (Archiver.Open_Archive (A, "file.zip"));
>  X : Integer;
>
> begin
>  X := Integer'Input (S);
>
>  Ada.Text_IO.Put_Line (Integer'Image (X));
> end Main;
>
>
> -- 
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42140
>
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-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42140