Problem where a function is invoked once but called twice (when invocation is within an allocator).

Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Rod Kay]

hi,

   Any clues on why the use of an allocator would cause a single
function invocation to be called twice ?


   the_Movie : media.Video.view := new_Movie;

   the_next_Frame :              openGL.Image :=
the_Movie.next_Frame;                                        -- case 1
   the_next_Frame : access openGL.Image := new
opengl.Image' (the_Movie.next_Frame);   -- case 2

   In the 1st case, the 'next_Frame' function is called once.
   In the 2nd case, it is called twice.


   'the_Movie' is an access to an object of tagged type
'media.Video.item'.

   package media.Video is
      type Item is tagged limited private;
      type View is access all Item;
      ...
      function  next_Frame  (Self : access Item) return opengl.Image;
      ...
   end media.Video;



   'opengl.Image' is an array with two unconstrained indices ...

   package openGL is
      ...
      type Image is array (Index_t range <>, Index_t range <>) of
Color;
   end openGL;



   In case it matters, the 'next_Frame' function contains a rendezvous
with a decoder task.
   The decoder task is a component of the 'media.Video.item' record.



regards,
Rod.

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[J-P. Rosen]

Le 05/05/2011 05:52, Rod Kay a �crit :
>     Any clues on why the use of an allocator would cause a single
> function invocation to be called twice ?
>
>
>     the_Movie : media.Video.view := new_Movie;
>
>     the_next_Frame :              openGL.Image :=
> the_Movie.next_Frame;                                        -- case 1
>     the_next_Frame : access openGL.Image := new
> opengl.Image' (the_Movie.next_Frame);   -- case 2
>
>     In the 1st case, the 'next_Frame' function is called once.
>     In the 2nd case, it is called twice.
>

Wouldn't Image be controlled by any chance? In that case, the assignment 
may involve the creation of an intermediate object
-- 
---------------------------------------------------------
            J-P. Rosen (rosen@adalog.fr)
Adalog a d�m�nag� / Adalog has moved:
2 rue du Docteur Lombard, 92441 Issy-les-Moulineaux CEDEX
Tel: +33 1 45 29 21 52, Fax: +33 1 45 29 25 00

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Rod Kay]

On May 5, 3:43 pm, "J-P. Rosen" <ro...@adalog.fr> wrote:
>
> Wouldn't Image be controlled by any chance? In that case, the assignment
> may involve the creation of an intermediate object

   Not in this case, no.

   'opengl.Image' is fairly simple array type with 2 unconstrained
indices ...

   type Image is array (Index_t range <>, Index_t range <>) of Color;

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Yannick Duchêne (Hibou57)]

Le Thu, 05 May 2011 07:43:08 +0200, J-P. Rosen <rosen@adalog.fr> a écrit:
> Wouldn't Image be controlled by any chance? In that case, the assignment  
> may involve the creation of an intermediate object
Even if this was, this would not be a reason for “the_Movie.next_Frame” to  
be invoked twice.

Rod, may be you should have a look at the produced assembly ? and post an  
excerpt here

-- 
Si les chats miaulent et font autant de vocalises bizarres, c’est pas pour  
les chiens.
“ c++; /* this makes c bigger but returns the old value */ ” [Anonymous]

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Rod Kay]

On May 5, 6:22 pm, Yannick Duchêne (Hibou57)
<yannick_duch...@yahoo.fr> wrote:
>
> Rod, may be you should have a look at the produced assembly ? and post an  
> excerpt here

   A good idea.

   I created a small test program ...


with media.Video;
with openGL;

procedure Tester
is
   the_Movie : media.Video.view := media.Video.new_Video ("xyz.avi");

   Case_1 :        openGL.Image := the_Movie.next_Frame;
   Case_2 : access openGL.Image := new
opengl.Image' (the_Movie.next_Frame);
begin
   null;
end;


   ... and generated the mixed ada/asm, which is here:
http://109.74.196.91:8080/doubled_next_Frame_call_results.txt


   In brief, the mixed ada/asm shows next_Frame being called twice for
Case_2 ...


****    Case_2 : access openGL.Image := new
opengl.Image' (the_Movie.next_Frame);
   ...
   call	media__video__next_frame
   ...
   call	__gnat_malloc
   ...
   call	media__video__next_frame
   ...
   call	memcpy



   Hope this helps.

regards.

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Florian Weimer]

* Rod Kay:

>    ... and generated the mixed ada/asm, which is here:
> http://109.74.196.91:8080/doubled_next_Frame_call_results.txt

Could you show the -gnatG output as well?

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Rod Kay]

On May 6, 3:07 am, Florian Weimer <f...@deneb.enyo.de> wrote:
>
> Could you show the -gnatG output as well?

Source recreated from tree for Tester (body)
--------------------------------------------

with media;
with media.media__video;
with opengl;
with ada.ada__tags;
with system.system__secondary_stack;

procedure tester is
   M13b : system__secondary_stack__mark_id :=
     $system__secondary_stack__ss_mark;

   procedure tester___clean is
   begin
      $system__secondary_stack__ss_release (M13b);
      return;
   end tester___clean;
begin
   the_movie : media.media__video.media__video__view := media.
     media__video.media__video__new_video__2 ("xyz.avi");
   [constraint_error when
     the_movie = null
     "access check failed"]

   -- Case 1 begins here ...
   type tester__A3b is access all opengl__image;
   R4b : constant tester__A3b := media__video__next_frame (the_movie,
     selfL => 0)'reference;
   subtype tester__Tcase_1S is opengl__image (R4b.all'first(1) ..
R4b.all'
     last(1), R4b.all'first(2) .. R4b.all'last(2));
   [constraint_error when
     R4b.all'last(2) >= R4b.all'first(2) and then (R4b.all'first(2) <
       0 or else R4b.all'last(2) > 65535)
     "range check failed"]
   [constraint_error when
     R4b.all'last(1) >= R4b.all'first(1) and then (R4b.all'first(1) <
       0 or else R4b.all'last(1) > 65535)
     "range check failed"]
   case_1 : opengl__image (R4b.all'first(1) .. R4b.all'last(1),
R4b.all'
     first(2) .. R4b.all'last(2)) := R4b.all;

   -- Case 2 begins here ...
   type tester__A10b is access all opengl__image;
   R11b : constant tester__A10b := (media__video__next_frame
(the_movie,
     selfL => 0))'reference;
   subtype tester__A9b is opengl__image ((R11b.all)'first(1) ..
(R11b.all)'
     last(1), (R11b.all)'first(2) .. (R11b.all)'last(2));
   [constraint_error when
     (R11b.all)'last(2) >= (R11b.all)'first(2) and then ((R11b.all)'
       first(2) < 0 or else (R11b.all)'last(2) > 65535)
     "range check failed"]
   [constraint_error when
     (R11b.all)'last(1) >= (R11b.all)'first(1) and then ((R11b.all)'
       first(1) < 0 or else (R11b.all)'last(1) > 65535)
     "range check failed"]
   case_2 : access opengl.opengl__image := new opengl.opengl__image'(
     tester__A9b?((media__video__next_frame (the_movie, selfL =>
0))));
   [subtype tester__T6b is access opengl__image]
   reference tester__T6b
   null;
   return;
at end
   tester___clean;
end tester;



   For Case_2, it appears the 1st call to next_Frame is used purely to
get the bounds of the returned array. The bounds are then used to
define 'tester__A9b' which is a subtype of opengl.Image of the correct
size. 'tester__A9b' is then used to convert the result of the 2nd call
to next_Frame, during allocation.

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Anh Vo]

On May 5, 5:49 pm, Rod Kay <rod....@aulace.com> wrote:
> On May 6, 3:07 am, Florian Weimer <f...@deneb.enyo.de> wrote:
>

> > Could you show the -gnatG output as well?
>
> Source recreated from tree for Tester (body)
> --------------------------------------------
>
> with media;
> with media.media__video;
> with opengl;
> with ada.ada__tags;
> with system.system__secondary_stack;
>
> procedure tester is
>    M13b : system__secondary_stack__mark_id :=
>      $system__secondary_stack__ss_mark;
>
>    procedure tester___clean is
>    begin
>       $system__secondary_stack__ss_release (M13b);
>       return;
>    end tester___clean;
> begin
>    the_movie : media.media__video.media__video__view := media.
>      media__video.media__video__new_video__2 ("xyz.avi");
>    [constraint_error when
>      the_movie = null
>      "access check failed"]
>
>    -- Case 1 begins here ...
>    type tester__A3b is access all opengl__image;
>    R4b : constant tester__A3b := media__video__next_frame (the_movie,
>      selfL => 0)'reference;
>    subtype tester__Tcase_1S is opengl__image (R4b.all'first(1) ..
> R4b.all'
>      last(1), R4b.all'first(2) .. R4b.all'last(2));
>    [constraint_error when
>      R4b.all'last(2) >= R4b.all'first(2) and then (R4b.all'first(2) <
>        0 or else R4b.all'last(2) > 65535)
>      "range check failed"]
>    [constraint_error when
>      R4b.all'last(1) >= R4b.all'first(1) and then (R4b.all'first(1) <
>        0 or else R4b.all'last(1) > 65535)
>      "range check failed"]
>    case_1 : opengl__image (R4b.all'first(1) .. R4b.all'last(1),
> R4b.all'
>      first(2) .. R4b.all'last(2)) := R4b.all;
>
>    -- Case 2 begins here ...
>    type tester__A10b is access all opengl__image;
>    R11b : constant tester__A10b := (media__video__next_frame
> (the_movie,
>      selfL => 0))'reference;
>    subtype tester__A9b is opengl__image ((R11b.all)'first(1) ..
> (R11b.all)'
>      last(1), (R11b.all)'first(2) .. (R11b.all)'last(2));
>    [constraint_error when
>      (R11b.all)'last(2) >= (R11b.all)'first(2) and then ((R11b.all)'
>        first(2) < 0 or else (R11b.all)'last(2) > 65535)
>      "range check failed"]
>    [constraint_error when
>      (R11b.all)'last(1) >= (R11b.all)'first(1) and then ((R11b.all)'
>        first(1) < 0 or else (R11b.all)'last(1) > 65535)
>      "range check failed"]
>    case_2 : access opengl.opengl__image := new opengl.opengl__image'(
>      tester__A9b?((media__video__next_frame (the_movie, selfL =>
> 0))));
>    [subtype tester__T6b is access opengl__image]
>    reference tester__T6b
>    null;
>    return;
> at end
>    tester___clean;
> end tester;
>
>    For Case_2, it appears the 1st call to next_Frame is used purely to
> get the bounds of the returned array. The bounds are then used to
> define 'tester__A9b' which is a subtype of opengl.Image of the correct
> size. 'tester__A9b' is then used to convert the result of the 2nd call
> to next_Frame, during allocation.

What compiler do you use? Do you mind to post the complete (minimum
required) source. I would like to see if I get the same result on my
machine.

Anh Vo

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Rod Kay]

On May 7, 9:41 am, Anh Vo <anhvofrc...@gmail.com> wrote:
>
> What compiler do you use? Do you mind to post the complete (minimum
> required) source. I would like to see if I get the same result on my
> machine.
>
> Anh Vo


   I'm using the GPL10 edition of Gnat on Ubuntu 10.04 (32bit).

   Here's a tarball of the testcase ... http://109.74.196.91:8080/double_next_frame_call.tar.gz

   You may need to install ffmpeg development packages (libavutil-dev,
libswscale-dev, libavcodec-dev, libavformat-dev on debian/ubuntu).

   Also, it should be built with gprbuild.

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Georg Bauhaus]

On 5/7/11 3:38 AM, Rod Kay wrote:

>     I'm using the GPL10 edition of Gnat on Ubuntu 10.04 (32bit).
>
>     Here's a tarball of the testcase ... http://109.74.196.91:8080/double_next_frame_call.tar.gz
>
>     You may need to install ffmpeg development packages (libavutil-dev,
> libswscale-dev, libavcodec-dev, libavformat-dev on debian/ubuntu).
>
>     Also, it should be built with gprbuild.

First, I can confirm that on Mac OS X the assembly listing
of tester shows three calls, too:

$ grep _media__video__next_frame build/tester.s
	call	_media__video__next_frame
	call	_media__video__next_frame
	call	_media__video__next_frame
$

(I've had to make a few changes to c_media due to recent
changes in ffmpeg, viz. definitions CODEC_TYPE_VIDEO and
others seem to have been replaced with AVMEDIA_TYPE_VIDEO
and others; avcodec_decode_video2 is new for
avcodec_decode_video. Just grabbed patches from ffmpeg
clients from the net, I don't understand them.)

The following appears to be generating two calls only, FWIW:

    the_Movie : media.Video.view := media.Video.new_Video ("xyz.avi");

    Case_1 :        openGL.Image := the_Movie.next_Frame;
    Workaround :    openGL.Image renames The_Movie.Next_Frame;
    Case_2 : access openGL.Image := new opengl.Image' (Workaround);
  
$ grep _media__video__next_frame build/tester.s
	call	_media__video__next_frame
	call	_media__video__next_frame
$

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Rod Kay]

On May 7, 7:06 pm, Georg Bauhaus <rm.dash-bauh...@futureapps.de>
wrote:
>
> First, I can confirm that on Mac OS X the assembly listing
> of tester shows three calls, too:
>
> $ grep _media__video__next_frame build/tester.s
>         call    _media__video__next_frame
>         call    _media__video__next_frame
>         call    _media__video__next_frame
> $

   Thanks for the info.


> The following appears to be generating two calls only, FWIW:
>
>     the_Movie : media.Video.view := media.Video.new_Video ("xyz.avi");
>
>     Case_1 :        openGL.Image := the_Movie.next_Frame;
>     Workaround :    openGL.Image renames The_Movie.Next_Frame;
>     Case_2 : access openGL.Image := new opengl.Image' (Workaround);
>

   Heh, this is indeed how I ended up tackling the problem in the real
source :).

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Anh Vo]

On May 6, 6:38 pm, Rod Kay <rod....@aulace.com> wrote:
> On May 7, 9:41 am, Anh Vo <anhvofrc...@gmail.com> wrote:
>
>
>
> > What compiler do you use? Do you mind to post the complete (minimum
> > required) source. I would like to see if I get the same result on my
> > machine.
>
> > Anh Vo
>
>    I'm using the GPL10 edition of Gnat on Ubuntu 10.04 (32bit).
>
>    Here's a tarball of the testcase ...http://109.74.196.91:8080/double_next_frame_call.tar.gz
>
>    You may need to install ffmpeg development packages (libavutil-dev,
> libswscale-dev, libavcodec-dev, libavformat-dev on debian/ubuntu).
>
>    Also, it should be built with gprbuild.

Thank you for posting the code. However, I had problem to download
this tar file. Any one else had problem as I did?

Anh Vo

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Dan]

Here's a simpler test case.  Taking out the Pragma Pack makes it work.

package Media is

   type Color is
      record
         val : integer;
      end record;

   type Image is array (integer range <>) of Color;
   pragma pack (Image);         -- matters!

   function next_Frame return Image;

end Media;

with Ada.Text_IO; use Ada.Text_IO;
package body Media is
   counter: integer := 0;

   function next_Frame return Image is
   begin
      put_line("in next_frame");
      counter := counter + 1;
      return (1..10 => (val => counter));
   end next_Frame;

end Media;



with Media;
with text_io;
procedure Test1 is

   Case_1 :        Media.Image :=     Media.Image' (Media.next_Frame);
   Case_2 : access Media.Image := new Media.Image' (Media.next_Frame);
begin
   text_io.put_line(case_1(5).val'img);
   text_io.put_line(case_2(5).val'img);
end;

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Anh Vo]

On May 9, 4:00 pm, Dan <d...@irvine.com> wrote:
> Here's a simpler test case.  Taking out the Pragma Pack makes it work.
>
> package Media is
>
>    type Color is
>       record
>          val : integer;
>       end record;
>
>    type Image is array (integer range <>) of Color;
>    pragma pack (Image);         -- matters!
>
>    function next_Frame return Image;
>
> end Media;
>
> with Ada.Text_IO; use Ada.Text_IO;
> package body Media is
>    counter: integer := 0;
>
>    function next_Frame return Image is
>    begin
>       put_line("in next_frame");
>       counter := counter + 1;
>       return (1..10 => (val => counter));
>    end next_Frame;
>
> end Media;
>
> with Media;
> with text_io;
> procedure Test1 is
>
>    Case_1 :        Media.Image :=     Media.Image' (Media.next_Frame);
>    Case_2 : access Media.Image := new Media.Image' (Media.next_Frame);
> begin
>    text_io.put_line(case_1(5).val'img);
>    text_io.put_line(case_2(5).val'img);
> end;

Thank you for making the simplest test case.

I got double calls, too. It is absolutely a compiler bug.

Anh Vo

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Rod Kay]

On May 10, 9:00 am, Dan <d...@irvine.com> wrote:
> Here's a simpler test case.  Taking out the Pragma Pack makes it work.
>

   Ah, very nice, thank you.

   Yes, I also 'pragma pack' the openGL.Image type.

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Rod Kay]

On May 10, 10:14 am, Anh Vo <anhvofrc...@gmail.com> wrote:
>
> I got double calls, too. It is absolutely a compiler bug.
>

   Yes, I suppose it must be. It will be interesting to try it again
when GPL11 arrives.

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Anh Vo]

On May 9, 5:24 pm, Rod Kay <rod....@aulace.com> wrote:
> On May 10, 10:14 am, Anh Vo <anhvofrc...@gmail.com> wrote:
>
> > I got double calls, too. It is absolutely a compiler bug.
>
>    Yes, I suppose it must be. It will be interesting to try it again
> when GPL11 arrives.

Have you sent a bug report yet? I hope you did if you want to see it
fix in GNAT-GPL-2011.

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Dan]

Here's a version of the test case that fails in Ada83 mode.


package Media is

   type Color is
      record
         val : integer;
      end record;

   type Image is array (integer range <>) of Color;
   pragma pack (Image);         -- matters!

   function next_Frame return Image;

   type Image_ptr is access Media.Image;

end Media;

with Text_IO; use Text_IO;
package body Media is
   counter: integer := 0;

   function next_Frame return Image is
   begin
      put_line("in next_frame");
      counter := counter + 1;
      return (1 .. 5-counter => (val => 10));
   end next_Frame;

end Media;



with Media;
with text_io;
procedure Test2 is

   Case_1 : Media.Image(1..4) :=     Media.Image' (Media.next_Frame);
   Case_2 : Media.Image_ptr   := new Media.Image' (Media.next_Frame);

   procedure put(x: Media.Image) is
   j: integer;
   begin
     for i in x'range loop
        text_io.put_line(x(i).val'img);
        j := 1/x(i).val;        -- ensure val is not zero
     end loop;
     text_io.new_line;
   end;

begin
   put(case_1);
   put(case_2.all);
end;

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Rod Kay]

On May 10, 10:55 am, Anh Vo <anhvofrc...@gmail.com> wrote:
>
> Have you sent a bug report yet? I hope you did if you want to see it
> fix in GNAT-GPL-2011.

   One has been sent now (thank you Jesse Lang).

   And thanks to all who've replied and to Dan for taking the time to
simplify the test case.

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Ludovic Brenta]

Rod Kay writes on comp.lang.ada:
> On May 10, 10:55 am, Anh Vo wrote:
>> Have you sent a bug report yet? I hope you did if you want to see it
>> fix in GNAT-GPL-2011.
>
>    One has been sent now (thank you Jesse Lang).
>
>    And thanks to all who've replied and to Dan for taking the time to
> simplify the test case.

I would like this bug report to be public in the GCC bugzilla database;
for multiple reasons, this is better than for the bug to remain private
in AdaCore's bug tracking system.  Could someone take the time to file
it properly in Bugzilla?

-- 
Ludovic Brenta.

Re: Problem where a function is invoked once but called twice (when invocation is within an allocator).

[Rod Kay]

On May 14, 3:40 am, Ludovic Brenta <ludo...@ludovic-brenta.org> wrote:
>
> I would like this bug report to be public in the GCC bugzilla database;
> for multiple reasons, this is better than for the bug to remain private
> in AdaCore's bug tracking system.  Could someone take the time to file
> it properly in Bugzilla?
>

   Submitted ... http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48995

regards.