Allegro Manual: Reducing your executable size

# Reducing your executable size

Some people complain that Allegro produces very large executables. This is certainly true: with the DJGPP version, a simple "hello world" program will be about 200k, although the per-executable overhead is much less for platforms that support dynamic linking. But don't worry, Allegro takes up a relatively fixed amount of space, and won't increase as your program gets larger. As George Foot so succinctly put it, anyone who is concerned about the ratio between library and program code should just get to work and write more program code to catch up :-)

Having said that, there are several things you can do to make your programs smaller:

- For all platforms, you can use an executable compressor called UPX, which is available at http://upx.sourceforge.net/. This usually manages a compression ratio of about 40%.
- When using DJGPP: for starters, read the DJGPP FAQ section 8.14, and take note of the -s switch. And don't forget to compile your program with optimisation enabled!
- If a DOS program is only going to run in a limited number of graphics modes, you can specify which graphics drivers you would like to include with the code:

  >        BEGIN_GFX_DRIVER_LIST
  >           driver1
  >           driver2
  >           etc...
  >        END_GFX_DRIVER_LIST

  where the driver names are any of the defines:

  >        GFX_DRIVER_VBEAF
  >        GFX_DRIVER_VGA
  >        GFX_DRIVER_MODEX
  >        GFX_DRIVER_VESA3
  >        GFX_DRIVER_VESA2L
  >        GFX_DRIVER_VESA2B
  >        GFX_DRIVER_XTENDED
  >        GFX_DRIVER_VESA1

  This construct must be included in only one of your C source files. The ordering of the names is important, because the autodetection routine works down from the top of the list until it finds the first driver that is able to support the requested mode. I suggest you stick to the default ordering given above, and simply delete whatever entries you aren't going to use.
- If your DOS program doesn't need to use all the possible color depths, you can specify which pixel formats you want to support with the code:

  >        BEGIN_COLOR_DEPTH_LIST
  >           depth1
  >           depth2
  >           etc...
  >        END_COLOR_DEPTH_LIST

  where the color depth names are any of the defines:

  >        COLOR_DEPTH_8
  >        COLOR_DEPTH_15
  >        COLOR_DEPTH_16
  >        COLOR_DEPTH_24
  >        COLOR_DEPTH_32

  Removing any of the color depths will save quite a bit of space, with the exception of the 15 and 16-bit modes: these share a great deal of code, so if you are including one of them, there is no reason not to use both. Be warned that if you try to use a color depth which isn't in this list, your program will crash horribly!
- In the same way as the above, you can specify which DOS sound drivers you want to support with the code:

  >        BEGIN_DIGI_DRIVER_LIST
  >           driver1
  >           driver2
  >           etc...
  >        END_DIGI_DRIVER_LIST

  using the digital sound driver defines:

  >        DIGI_DRIVER_SOUNDSCAPE
  >        DIGI_DRIVER_AUDIODRIVE
  >        DIGI_DRIVER_WINSOUNDSYS
  >        DIGI_DRIVER_SB

  and for the MIDI music:

  >        BEGIN_MIDI_DRIVER_LIST
  >           driver1
  >           driver2
  >           etc...
  >        END_MIDI_DRIVER_LIST

  using the MIDI driver defines:

  >        MIDI_DRIVER_AWE32
  >        MIDI_DRIVER_DIGMID
  >        MIDI_DRIVER_ADLIB
  >        MIDI_DRIVER_MPU
  >        MIDI_DRIVER_SB_OUT

  If you are going to use either of these sound driver constructs, you must include both.
- Likewise for the DOS joystick drivers, you can declare an inclusion list:

  >        BEGIN_JOYSTICK_DRIVER_LIST
  >           driver1
  >           driver2
  >           etc...
  >        END_JOYSTICK_DRIVER_LIST

  using the joystick driver defines:

  >        JOYSTICK_DRIVER_WINGWARRIOR
  >        JOYSTICK_DRIVER_SIDEWINDER
  >        JOYSTICK_DRIVER_GAMEPAD_PRO
  >        JOYSTICK_DRIVER_GRIP
  >        JOYSTICK_DRIVER_STANDARD
  >        JOYSTICK_DRIVER_SNESPAD
  >        JOYSTICK_DRIVER_PSXPAD
  >        JOYSTICK_DRIVER_N64PAD
  >        JOYSTICK_DRIVER_DB9
  >        JOYSTICK_DRIVER_TURBOGRAFX
  >        JOYSTICK_DRIVER_IFSEGA_ISA
  >        JOYSTICK_DRIVER_IFSEGA_PCI
  >        JOYSTICK_DRIVER_IFSEGA_PCI_FAST

  The standard driver includes support for the dual joysticks, increased numbers of buttons, Flightstick Pro, and Wingman Extreme, because these are all quite minor variations on the basic code.
- If you are _really_ serious about this size, thing, have a look at the top of include/allegro/alconfig.h and you will see the lines:

  >        #define ALLEGRO_COLOR8
  >        #define ALLEGRO_COLOR16
  >        #define ALLEGRO_COLOR24
  >        #define ALLEGRO_COLOR32

  If you comment out any of these definitions and then rebuild the library, you will get a version without any support for the absent color depths, which will be even smaller than using the DECLARE_COLOR_DEPTH_LIST() macro. Removing the ALLEGRO_COLOR16 define will get rid of the support for both 15 and 16-bit hicolor modes, since these share a lot of the same code.

Note: the aforementioned methods for removing unused hardware drivers only apply to statically linked versions of the library, eg. DOS. On Windows and Unix platforms, you can build Allegro as a DLL or shared library, which prevents these methods from working, but saves so much space that you probably won't care about that. Removing unused color depths from alconfig.h will work on any platform, though.

If you are distributing a copy of the setup program along with your game, you may be able to get a dramatic size reduction by merging the setup code into your main program, so that only one copy of the Allegro routines will need to be linked. See setup.txt for details. In the DJGPP version, after compressing the executable, this will probably save you about 200k compared to having two separate programs for the setup and the game itself.

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