[Bug] [A5.1] Allegro crashes in fullscreen mode (rel. al_init_ttf_addon)

no-reply@allegro.cc (Max Savenkov) — Wed, 24 Jul 2013 12:17:44 +0000

I saw this reported already, but details were sketchy.

Allegro crashes sometimes under Windows when using DirectX render in full-screen mode with non-desktop resolution. Crash seems to be related to TTF addon. Here's my reproduction code:

#SelectExpand
  1  al_init();
  2
  3  al_set_new_bitmap_flags( ALLEGRO_MIN_LINEAR | ALLEGRO_MAG_LINEAR | ALLEGRO_MIPMAP | ALLEGRO_VIDEO_BITMAP );
  4
  5  al_set_new_display_flags( ALLEGRO_FULLSCREEN|ALLEGRO_DIRECT3D );
  6  al_set_new_display_option( ALLEGRO_VSYNC, 1, ALLEGRO_SUGGEST );
  7  al_set_new_display_option( ALLEGRO_COLOR_SIZE, 32, ALLEGRO_REQUIRE );
  8
  9  ALLEGRO_DISPLAY *d = al_create_display(1024, 768);
 10        if ( !d ) return;
 11
 12  al_init_image_addon();
 13  al_init_font_addon();  
 14  al_init_ttf_addon();
 15
 16  ALLEGRO_BITMAP *b = al_load_bitmap( "../Data/Sprites/defence_arrows.png" );  
 17
 18  al_flip_display();
 19
 20  al_destroy_bitmap( b );
 21  al_destroy_display( d );

Allegro (or rather DirectX) will crash in call from al_load_bitmap to here:

#SelectExpand
  1static void d3d_do_upload(ALLEGRO_BITMAP *bmp, int x, int y, int width,
  2   int height, bool sync_from_memory)
  3{
  4   ALLEGRO_BITMAP_EXTRA_D3D *d3d_bmp = get_extra(bmp);
  5
  6   if (sync_from_memory) {
  7      d3d_sync_bitmap_texture(bmp, x, y, width, height);
  8   }
  9
 10   if (_al_d3d_render_to_texture_supported()) {
 11      if (d3d_bmp->display->device->UpdateTexture(
 12            (IDirect3DBaseTexture9 *)d3d_bmp->system_texture,
 13            (IDirect3DBaseTexture9 *)d3d_bmp->video_texture) != D3D_OK) {
 14         ALLEGRO_ERROR("d3d_do_upload: Couldn't update texture.\n");
 15         return;
 16      }
 17   }
 18}

...on call to d3d_bmp->display->device->UpdateTexture on attempt to access invalid pointer. Bot input pointers seem to be valid at the first glance, so something deeper is corrupted.

However, this will not happen, if I initialize ttf addon BEFORE creating display:

#SelectExpand
  1  al_init();
  2
  3  al_set_new_bitmap_flags( ALLEGRO_MIN_LINEAR | ALLEGRO_MAG_LINEAR | ALLEGRO_MIPMAP | ALLEGRO_VIDEO_BITMAP );
  4
  5  al_set_new_display_flags( ALLEGRO_FULLSCREEN|ALLEGRO_DIRECT3D );
  6  al_set_new_display_option( ALLEGRO_VSYNC, 1, ALLEGRO_SUGGEST );
  7  al_set_new_display_option( ALLEGRO_COLOR_SIZE, 32, ALLEGRO_REQUIRE );
  8
  9  al_init_image_addon();
 10  al_init_font_addon();  
 11  al_init_ttf_addon();
 12
 13  ALLEGRO_DISPLAY *d = al_create_display(1024, 768);
 14        if ( !d ) return;
 15
 16  ALLEGRO_BITMAP *b = al_load_bitmap( "../Data/Sprites/defence_arrows.png" );  
 17
 18  al_flip_display();
 19
 20  al_destroy_bitmap( b );
 21  al_destroy_display( d );

This way, it always works. However, I could find no mention of this in docs, and also this does not happen if I either:

Use OpenGL or
Use windowed mode or
Use fullscreen mode with desktop resolution (1920x1080 for me)

So I think it's a bug.

no-reply@allegro.cc (Trent Gamblin) — Wed, 24 Jul 2013 12:48:28 +0000

This is al_init_ttf_addon, so to me it looks like something in Freetype itself:

#SelectExpand
  1bool al_init_ttf_addon(void)
  2{
 if (ttf_inited) {
    ALLEGRO_WARN("TTF addon already initialised.\n");
    return true;
 }
  7
 FT_Init_FreeType(&ft);
 vt.font_height = ttf_font_height;
 vt.font_ascent = ttf_font_ascent;
 vt.font_descent = ttf_font_descent;
 vt.char_length = ttf_char_length;
 vt.text_length = ttf_text_length;
 vt.render_char = ttf_render_char;
 vt.render = ttf_render;
 vt.destroy = ttf_destroy;
 vt.get_text_dimensions = ttf_get_text_dimensions;
 vt.get_font_ranges = ttf_get_font_ranges;
 19
 al_register_font_loader(".ttf", al_load_ttf_font);
 21
 /* Can't fail right now - in the future we might dynamically load
  * the FreeType DLL here and/or initialize FreeType (which both
  * could fail and would cause a false return).
  */
 ttf_inited = true;
 return ttf_inited;
 28}

no-reply@allegro.cc (Max Savenkov) — Thu, 25 Jul 2013 11:02:55 +0000

I suspect race condition or some other synchronization problem somewhere. If I place a unneeded call to al_flip_display before addon initialization, code stop crashing:

  ALLEGRO_DISPLAY *d = al_create_display(1024, 768);

  al_flip_display();
  al_init_image_addon();
  al_init_font_addon();
  al_init_ttf_addon();

  ALLEGRO_BITMAP *b = al_load_bitmap( "../Data/Sprites/defence_arrows.png" 
  al_flip_display();
);

However, adding al_rest( 10.0 ) instead of al_flip_display do not help.

I noticed that when I try to set non-desktop resolution in fullscreen mode, display creation takes a longer time. Maybe this crash has something to do with it.