Possible memory leak in allegro 5.0.10

no-reply@allegro.cc (Aikei_c) — Fri, 16 Aug 2013 13:03:22 +0000

OK, here is the code I (mostly) took from wiki:

#SelectExpand
  1#define CRTDBG_MAP_ALLOC
  2#include 
  3#include 
  4
  5#include "allegro5/allegro.h"
  6#include "allegro5/allegro_image.h"
  7#include "allegro5/allegro_native_dialog.h"
  8
  9int main(int argc, char **argv)
 10{
_CrtSetDbgFlag ( _CRTDBG_ALLOC_MEM_DF |_CRTDBG_LEAK_CHECK_DF );
ALLEGRO_DISPLAY *display = NULL;
ALLEGRO_BITMAP  *image   = NULL;

if(!al_init()) 
{
  al_show_native_message_box(display, "Error", "Error", "Failed to initialize allegro!", 
                NULL, ALLEGRO_MESSAGEBOX_ERROR);
  return 0;
}

if(!al_init_image_addon()) 
{
  al_show_native_message_box(display, "Error", "Error", "Failed to initialize al_init_image_addon!", 
                NULL, ALLEGRO_MESSAGEBOX_ERROR);
  return 0;
}

display = al_create_display(800,600);

if(!display) 
{
  al_show_native_message_box(display, "Error", "Error", "Failed to initialize display!", 
                NULL, ALLEGRO_MESSAGEBOX_ERROR);
  return 0;
}

image = al_load_bitmap("image.png");

if(!image) 
{
  al_show_native_message_box(display, "Error", "Error", "Failed to load image!", 
                  NULL, ALLEGRO_MESSAGEBOX_ERROR);
  al_destroy_display(display);
  return 0;
}

al_draw_bitmap(image,200,200,0);

al_flip_display();
al_rest(2);

al_destroy_display(display);
al_destroy_bitmap(image);
al_shutdown_image_addon();
al_uninstall_system();
 57
return 0;
 59}

I also added the _CrtSetDbgFlag ( _CRTDBG_ALLOC_MEM_DF |_CRTDBG_LEAK_CHECK_DF ) line which is a crt function which spots memory leaks and dumps them to output at program termination (http://msdn.microsoft.com/en-us/library/vstudio/x98tx3cf.aspx)
When the program terminates, I get the following output:

Detected memory leaks!

Dumping objects -> {564} normal block at 0x007CB008, 65536 bytes long. Data: <+Da +Da +Da +Da > 2B 44 61 FF 2B 44 61 FF 2B 44 61 FF 2B 44 61 FF Object dump complete.

I then set a breakpoint at block 564 allocation, and this block is allocated when allegro bitmap is loaded, specifically, in _al_d3d_create_bitmap(), you can see attachment to get the idea where it is.

Memory for d3d bitmap is probably not deallocated at program termination, despite explicit call to allegro_destroy_bitmap().

Or it may be false positive.

no-reply@allegro.cc (Arthur Kalliokoski) — Fri, 16 Aug 2013 13:10:18 +0000

65536 bytes! Zomg!

no-reply@allegro.cc (Aikei_c) — Fri, 16 Aug 2013 13:14:26 +0000

Actually, there must be an error in this tutorial: http://wiki.allegro.cc/index.php?title=Basic_tutorial_on_loading_and_showing_images
When I free the image BEFORE freeing the display (which uses this image, probably), no memory leaks are detected.
I must say, though, that it is not specified anywhere, although seems natural. However, this tutorial really confused me.

P.S.: Can I edit the order of these calls in wiki?

no-reply@allegro.cc (Vanneto) — Fri, 16 Aug 2013 20:33:48 +0000

Of course you can. Any contribution to the wiki is welcome and appreciated.

no-reply@allegro.cc (Matthew Leverton) — Fri, 16 Aug 2013 21:30:17 +0000

When you destroy the display first, the bitmap is converted to a memory bitmap. So perhaps that process is leaking some memory.

no-reply@allegro.cc (beoran) — Sun, 18 Aug 2013 11:57:36 +0000

It shouldn't though. If no one else takes this, I'll look into it after my holiday.

no-reply@allegro.cc (Thomas Fjellstrom) — Sun, 18 Aug 2013 12:08:18 +0000

Holidays are the perfect time to work on side projects.

no-reply@allegro.cc (beoran) — Sun, 18 Aug 2013 12:22:51 +0000

Unfortunately, not so if they are family holidays. Ah well, that's what it's like to be a father.

no-reply@allegro.cc (Thomas Fjellstrom) — Sun, 18 Aug 2013 12:38:54 +0000

Nah, nothing says you actually have to spend all of your time on a holiday catering to your family