GBDK 2020 Docs  4.2.0
API Documentation for GBDK 2020
GBDK Release Notes

The GBDK-2020 releases can be found on Github:

GBDK-2020 Release Notes

GBDK-2020 4.2


  • Includes SDCC version ~4.3 with GBDK-2020 patches for Z80 and NES
  • Known Issues
  • Library
  • Toolchain / Utilities
    • Added png2hicolorgb
    • lcc
      • Fixed --sdccbindir
      • Removed the unused -DINT_16_BITS from the default SDCC compiler and preprocessor arguments
      • Improved improved Game Gear header compatibility (change header region code from 4 to 6)
    • png2asset
      • Added -o as a more standard version of the -c argument
      • Added -repair_index_pal: Tries to repair tile palettes for indexed color pngs (such as when RGB paint programs mix up indexed colors if the same color exists in multiple palettes). Implies -keep_palette_order
      • Added -no_palettes: Do not export palette data
      • Fixed support for indexed color pngs with less than 8 bits color depth
      • Fixed incorrect palettes when different colors have same luma value (use RGB values as less-significant bits)
      • Fixed -keep_duplicate_tiles not working with -source_tileset
      • Changed to use cross-platform constants for metasprite properties (S_FLIPX, S_FLIPY and S_PAL)
    • makebin
      • Warn if RAM banks specified and file size of ROM is less than the 64K required to enable them with in emulators
    • Added sdld6808 (for NES)
  • Examples
    • Fixed mkdir broken in some compile.bat files (remove unsupported -p flag during bat file conversion)
    • Sound Test: Added MegaDuck support
    • Wav Playback: Improved support on AGB/AGS hardware
    • Metasprites: Added sub-palette switching for GBC and NES, software metasprite flipping for sms/gg
    • Large Map: Added color for supported platforms
    • LCD ISR Wobble: Improved interrupt flag settings
    • Added GB-Type example
    • Added Game Boy Color Hi-Color example using png2hicolorgb
  • Docs:

GBDK-2020 4.1.1


  • Includes SDCC version 13350 with GBDK-2020 patches for Z80
  • Library

GBDK-2020 4.1.0


  • Includes SDCC version 13350 with GBDK-2020 patches for Z80
  • Known Issues
    • The compile.bat batch files for Windows use the an invalid -p option for mkdir
  • Building GBDK
    • The linux port of SDCC is custom built on Ubuntu 16.04 due to reduced GLIBC compatibility issues in more recent SDCC project builds.
    • Added Windows 32-Bit build
  • Platforms
  • Licensing
    • Clarified licensing status with consent from GBDK original authors, added licensing folder to distribution
  • Library
  • Toolchain / Utilities
    • lcc
      • Changed to Error out and warn when gbz80 port is used instead of sm83
    • png2asset
      • Added -tiles_only: Export tile data only
      • Added -maps_only: Export map tilemap only
      • Added -metasprites_only: Export metasprite descriptors only
      • Added -source_tileset: Use source tileset image with common tiles
      • Added -keep_duplicate_tiles: Do not remove duplicate tiles
      • Added -bin: Export to binary format (includes header files)
      • Added -transposed: Export transposed (column-by-column instead of row-by-row)
      • Added basic MSXDOS support
        • Added 1bpp packing mode (BPP1)
        • -spr16x16msx
      • Added basic NES support
        • -use_nes_attributes
        • -use_nes_colors
      • Changed to only export _tile_pals[] arrays when -use-structs is set (ZGB specific)
    • gbcompress
      • Added --bank=<num> Add Bank Ref: 1 - 511 (default is none, with --cout only)
      • Fixed failure to flush data at end of compression (uncommitted bytes)
      • Fixed Warning: File read size didn't match expected
    • lcc
      • When -autobank is specified lcc will automatically add -yoA for makebin if no -yo* entry is present
      • Fixed broken -E Preprocess only flag
    • makecom
      • Added makecom for post-processing msxdos binaries
    • makebin
    • bankpack
      • Added support for the Game Boy Camera MBC
      • Added -reserve=<bank>:<size> option to reserve space during autobank packing
        • Workaround for libraries that contain objects in banks (such as gbt-player)
    • ihxcheck
      • Check and warn for bank overflows under specific conditions
        • A multiple write to the same address must occur. The address where the overlap ends is used as BANK.
        • There must also be a write which spans multiple banks, the ending address of that must match BANK. The starting addresses is the OVERFLOW-FROM BANK.
  • Examples
    • Changed Logo example to use new GBDK logo art from user "Digit"
    • Added example for APA image mode with more than 256 tiles
    • Added SGB Sound Effects example
    • Changed to new WAV sound example
  • Docs
    • Added improved MBC Type chart
    • Include SDCC manual in pdf format
    • Various doc updates and improvements

GBDK-2020 4.0.6


  • Includes SDCC version 12539 with GBDK-2020 patches for Z80
  • Building GBDK
    • Changed to target older version of macOS (10.10) when building for better compatibility
  • Platforms
  • Library
  • Toolchain / Utilities
    • png2asset
      • Added SMS/GG graphics format support
      • Added 4bpp and SGB borders
      • Added warning when image size is not an even multiple of tile size
      • Added -tile_origin offset option for when map tiles do not start at tile 0 in VRAM
      • Added *_TILE_COUNT definition to output
      • Fixed CGB ...s_map_attributes type definition in output
      • Fixed values for num_palettes in output
      • Fixed incorrect TILE_COUNT value when not -using_structs
    • lcc
      • Changed makebin flags to turn off Nintendo logo copy for GB/CGB (use version in crt instead)
      • Fixed lcc handling of makebin -x* arguments
  • Examples
    • Added logo example (cross-platform)
    • Added ISR_VECTOR example of a raw ISR vector with no dispatcher for GB/CGB
    • Changed sgb_border example to use png2asset for graphics
    • Changed use of set_interrupts() in examples so it's outside critical sections (since it disables/enables interrupts)
    • Changed cross-platform auto-banks example to use .h header files
    • Changed SGB border example to also work with SGB on PAL SNES
  • Docs
    • Added new section: Migrating From Pre-GBDK-2020 Tutorials

GBDK-2020 4.0.5


  • Includes SDCC version 12539 with GBDK-2020 patches for Z80
  • Known Issues
    • SDCC: z80instructionSize() failed to parse line node, assuming 999 bytes
      • This is a known issue with the SDCC Peephole Optimizer parsing and can be ignored.
    • -bo<n> and -ba<n> are not supported by the Windows build of sdcc
    • On macOS the cross platform banks example has problems parsing the filename based ROM and RAM bank assignments into -bo<n> and -ba<n>
  • Added support for new consoles. See Supported Consoles & Cross Compiling
    • Analogue Pocket (ap)
    • Sega Master System (sms) and Game Gear (gg)
  • Library
  • Examples
    • Added cross-platform examples (build for multiple consoles: gb, ap, sms, gg)
    • Added sms, gg, pocket(ap) examples
    • Added incbin example
    • Added simple physics sub-pixel / fixed point math example
    • Added rle decompression example
    • Changed windows make.bat files to compile.bat
    • Bug fixes and updates for existing examples
  • Toolchain / Utilities
    • png2asset
      • png2asset is the new name for the png2mtspr utility
      • Added collision rectangle width and height (-pw, -ph)
      • Added option to use the palette from the source png (-keep_palette_order)
      • Added option to disable tile flip (-noflip)
      • Added export as map: tileset + bg (-map)
      • Added option to use CGB BG Map attributes (-use_map_attributes)
      • Added option to group the exported info into structs (-use_structs)
    • lcc
      • Use -m to select target port and platform: "-m[port]:[plat]" ports:gbz80,z80 plats:ap,gb,sms,gg
      • Changed default output format when not specified from .ihx to .gb (or other active rom extension)
      • Changed lcc to always use the linkerfile -lkout= option when calling bankpack
      • Fixed name generation crash when outfile lacks extension
    • bankpack
      • Added linkerfile input and output: -lkin=<file>, -lkout=<file>
      • Added selector for platform specific behavior plat=<plat> (Default:gb, Avaialble:gb,sms). sms/gg targets prohibits packing LIT_N areas in the same banks as CODE_N areas
      • Added randomization for auto-banks (-random) for debugging and testing
    • utility_gbcompress
      • Added C source array format output (–cout) (optional variable name argument –varname=)
      • Added C source array format input (–cin) (experimental)
      • Added block style rle compression and decompression mode: --alg=rle
      • Fixed comrpession errors when input size was larger than 64k
  • Docs

GBDK-2020 4.0.4


  • Library
  • Examples
    • Added project using a .lk linkerfile
    • Changed all examples to use standard stdint.h types
    • Moved banks_farptr and banks_new examples to "broken" due to SDCC changes
  • Toolchain / Utilities
    • png2mtspr
      • Added option to change default value for sprite property/attributes in (allows CGB palette, BG/WIN priority, etc).
      • Improved: Turn off suppression of "blank" metasprite frames (composed of entirely transparent sprites)
      • Fixed endless loop for png files taller than 255 pixels
    • bankpack
      • Fixed -yt mbc specifier to also accept Decimal
      • Improved: bank ID can be used in same file it is declared. Requires SDCC 12238+ with -n option to defer symbol resolution to link time.
    • gbcompress
      • Added C source input (experimental) and output
      • Added size #defines
    • lcc
      • Added -no-libs and -no-crt options
      • Added support for .lk linker files (useful when number of files on lcc command line exceeds max size on windows)
      • Added support for converting .ihx to .gb
      • Added rewrite .o files -> .rel for linking when called with -autobank and -Wb-ext=.rel
      • Workaround makebin -Wl-yp formatting segfault
  • Docs
    • Improved utility_png2mtspr documentation
    • Various doc updates and improvements

GBDK-2020 4.0.3


GBDK-2020 4.0.2


  • Includes SDCC snapshot build version 12016 (has a fix for duplicate debug symbols generated from inlined header functions which GBDK 4.0+ uses)
  • Updated documentation
  • Library was improved
    • Linking with stdio.h does not require that much ROM now
    • Default font is changed to the smaller one (102 characters), that leaves space for user tiles
    • Fixed broken support for multiplying longs
    • memset/memcpy minor enhancements
    • safer copy-to-VRAM functions
    • loading of 1bit data fixed, also now it is possible to specify pixel color
    • Improved code generation for the GBDK Library with SDCC switch on by default: --max-allocs-per-node 50000
    • fixed wrong parameter offsets in hiramcpy() (broken ram_function example)
    • Multiple minor improvements
  • New bankpack feature, allows automatic bank allocation for data and code, see banks_autobank example, feature is in beta state, use with care
  • Lcc improvements
    • Fixed option to specify alternate base addresses for shadow_OAM, etc
  • Examples: Added bgb debug example

GBDK-2020 4.0.1


  • Updated API documentation
  • IHX is checked for correctness before the makebin stage. That allows to warn about overwriting the same ROM addresses (SDCC toolchain does not check this anymore).
  • Library was improved
    • set_*_tiles() now wrap maps around horizontal and vertical boundaries correctly
    • new fill_*_rect() functions to clear rectangle areas
    • runtime initialization code now does not initialize whole WRAM with zeros anymore, that allows BGB to raise exceptions when code tries to read WRAM that was not written before.
    • enhanced SGB support
    • _current_bank variable is updated when using bank switching macros
    • Reorganized examples: each example is in separate folder now, that simplifies understanding.
    • Lcc improvements
      • Fix -S flag
      • Fix default stack location from 0xDEFF to 0xE000 (end of WRAM1)
      • Fix cleanup of .adb files with -Wf–debug flag
      • Fix output not working if target is -o some_filename.ihx

GBDK-2020 4.0


  • GBDK now requires SDCC 4.0.3 or higher, that has fully working toolchain. Old link-gbz80 linker is not used anymore, sdldgb and makebin are used to link objects and produce binary roms; maccer tool is no longer needed either
    • SDCC 4.0.3 has much better code generator which produces smaller and faster code. Code is twice faster
    • SOURCE LEVEL DEBUGGING is possible now! Native toolchain produces *.CDB files that contain detailed debug info. Look for EMULICIOUS extension for vs.code. It supports breakpoints, watches, inspection of local variables, and more!
    • SDCC 4.0.4 has fixed RGBDS support; library is not updated to support that in full yet, but it is possible to assemble and link code emitted by SDCC with RGDBS
    • New banked trampolines are used, they are faster and smaller
    • New (old) initialization for non-constant arrays do NOT require 5 times larger rom space than initialized array itself, SDCC even tries to compress the data
  • Library was improved
    • itoa/ltoa functions were rewritten, div/mod is not required now which is about 10 times faster
    • sprite functions are inline now, which is faster up to 12 times and produces the same or smaller code; .OAM symbol is renamed into _shadow_OAM that allows accessing shadow OAM directly from C code
    • interrupt handling was revised, it is now possible to make dedicated ISR's, that is important for time-sensitive handlers such as HBlank.
    • printf/sprintf were rewritten and splitted, print functions are twice faster now and also requre less rom space if you use sprintf() only, say, in bgb_emu.h
    • crash_handler.h - crash handler that allows to detect problems with ROMs after they are being released (adapted handler, originally written by ISSOtm)
    • improved and fixed string.h
    • many other improvements and fixes - thanks to all contributors!
  • Revised examples
  • Improved linux support
  • Lcc has been updated
    • it works with the latest version of sdcc
    • quoted paths with spaces are working now

GBDK-2020 3.2


  • Fixed OAM initialization that was causing a bad access to VRAM
  • Interrupt handlers now wait for lcd controller mode 0 or 1 by default to prevent access to inaccessible VRAM in several functions (like set_bkg_tiles)
  • Several optimizations here and there

GBDK-2020 3.1.1


  • Fixed issues with libgcc_s_dw2-1.dll

GBDK-2020 3.1


GBDK-2020 3.0.1


  • Updated SDCC to v.4.0
  • Updated LCC to work with the new compiler

GBDK-2020 3.0


  • Initial GBDK-2020 release
    Updated SDCC to v4.0 The new linker is not working so the old version is still there There is an issue with sdagb compiling drawing.s (the JP in line 32 after ".org .MODE_TABLE+4*.G_MODE" it's writing more than 4 bytes invading some addresses required by input.s:41) Because of this, all .s files in libc have been assembled with the old as-gbz80 and that's why it is still included

Historical GBDK Release Notes

GBDK 2.96

17 April, 2000
Many changes.

  • Code generated is now much more reliable and passes all of sdcc's regression suite.
  • Added support for large sets of local variables (>127 bytes).
  • Added full 32 bit long support.
  • Still no floating pt support.

GBDK 2.95-3

19th August, 2000

  • Stopped lcc with sdcc from leaking .cdb files all across /tmp.
  • Optimised < and > for 16 bit varibles.
  • Added a new lexer to sdcc. Compiling files with large initalised arrays takes 31% of the time (well, at least samptest.c does :)

This is an experimental release for those who feel keen. The main change is a new lexer (the first part in the compilation process which recognises words and symbols like '!=' and 'char' and turns them into a token number) which speeds up compilation of large initialised arrays like tile data by a factor of three. Please report any bugs that show up - this is a big change.

I have also included a 'minimal' release for win32 users which omits the documentation, library sources, and examples. If this is useful I will keep doing it.

GBDK 2.95-2

5th August, 2000
Just a small update. From the README:

  • Added model switching support –model-medium uses near (16 bit) pointers for data, and banked calls for anything not declared as 'nonbanked' –model-small uses near (16 bit) pointers for data and calls. Nothing uses banked calls. 'nonbanked' functions are still placed in HOME. Libraries are under lib/medium and lib/small.
  • Added the gbdk version to 'sdcc –version'
  • Changed the ways globals are exported, reducing the amount of extra junk linked in.
  • Turned on the optimisations in flex. Large constant arrays like tile data should compile a bit faster.

GBDK 2.95

22nd July, 2000

  • Fixed 'a << c' for c = [9..15]
  • no$gmb doesn't support labels of > 32 chars. The linker now trims all labels to 31 chars long.
  • Fixed wait_vbl for the case where you miss a vbl
  • Fixed + and - for any type where sizeof == 2 and one of the terms was on the stack. This includes pointers and ints. Fixes the text output bug in the examples. Should be faster now as well. Note that + and - for longs is still broken.
  • Fixed the missing */ in gb.h
  • Added basic far function support. Currently only works for isas and rgbasm. See examples/gb/far/*
  • bc is now only pushed if the function uses it. i.e. something like: int silly(int i) { return i; }
    will not have the push bc; pop bc around it.
  • Better rgbasm support. Basically: o Use "sdcc -mgbz80 --asm=rgbds file.c" for each file.c o Use "sdcc -mgbz80 --asm=rgbds crt0.o gbz80.lib gb.lib file1.o file2.o..."

to link everything together. The .lib files are generated using and sdcc to turn the gbdk libraries into something rgbds compatible. The libraries are not fully tested. Trust nothing. But give it a go :)

  • Ran a spell checker across the README and ChangeLog

This is a recommended upgrade. Some of the big features are:

Decent rgbds support. All the libraries and most of the examples can now compile with rgbds as the assembler. Banked function support. It is now easier to break the 32k barrier from within C. Functions can live in and be called transparently from any bank. Only works with rgbds Fixed some decent bugs with RSH, LSH, and a nasty bug with + and - for int's and pointers. Various optimisations in the code generator.

7th July, 2000
Information on float and long support. Someone asked about the state of float/long support recently. Heres my reply:

long support is partly there, as is float support. The compiler will correctly recognise the long and float keywords, and will generate the code for most basic ops (+, -, &, | etc) for longs correctly and will generate the function calls for floats and hard long operations (*, /, %) correctly. However it wont generate float constants in the correct format, nor will it 'return' a long or float - gbdk doesn't yet support returning types of 4 bytes. Unfortunately its not going to make it into 2.95 as there's too much else to do, but I should be able to complete long support for 2.96

GBDK 2.94

7th May, 2000
Many fixes - see the README for more.

7th May - Library documentation up. A good size part of the libraries that go with gbdk have been documented - follow the HTML link above to have a look. Thanks to quang for a good chunk of the gb.h documentation. Please report any errors :)

  • Fixed #define BLAH 7 // Unterminated ' error in sdcpp
    • Fixed SCY_REG += 2, SCY_REG -= 5 (add and subtract in indirect space) as they were both quite broken.
    • externs and static's now work as expected.
    • You can now specify which bank code should be put into using a #pragma e.g: #pragma bank=HOME Under rgbds and asxxxx putting code in the HOME bank will force the code into bank 0 - useful for library functions. The most recent #pragma bank= will be the one used for the whole file.
    • Fixed an interesting bug in the caching of lit addresses
    • Added support for accessing high registers directly using the 'sfr' directive. See libc/gb/sfr.s and gb/hardware.h for an example. It should be possible with a bit of work to make high ram directly usable by the compiler; at the moment it is experimental. You can test sfr's by enabling USE_SFR_FOR_REG=1
    • Added remove_VBL etc functions.
    • Documented the libs - see the gbdk-doc tarball distributed seperatly.
    • Two dimensional arrays seem to be broken.

GBDK 2.93

6th April, 2000
From the README

  • Added multi-bank support into the compiler - The old -Wf-boxx and -Wf-baxx options now work
  • Has preliminary support for generating rgbds and ISAS compatible assembler. Try -W–asm=rgbds or -W–asm=isas. The ISAS code is untested as I dont have access to the real assembler.
  • RSH is fixed
  • AND is fixed
  • The missing parts of 2.1.0's libs are there. Note: They are untested.
  • The dscan demo now fully works (with a hack :)
  • There is a bug with cached computed values which are later used as pointers. When the value is first used as a BYTE arg, then later as a pointer the pointer fails as the high byte was never computed and is now missing. A temporary fix is to declare something appropriate as 'volatile' to stop the value being cached. See dscan.c/bombs() for an example.

GBDK 2.92-2 for win32

26th March, 2000
This is a maintenance release for win32 which fixes some of the niggly install problems, especially:

  • win32 only. Takes care of some of the install bugs, including:
    • Now auto detects where it is installed. This can be overridden using set GBDKDIR=...
    • Problems with the installer (now uses WinZip)
    • Problems with the temp directory Now scans TMP, TEMP, TMPDIR and finally c: tmp
    • cygwin1.dll and 'make' are no longer required gbdk is now built using mingw32 which is win32 native make.bat is automagically generated from the Makefile
    • I've reverted to using WORD for signed 16 bit etc. GBDK_2_COMPAT is no longer required.

WORDS are now back to signed. GBDK_2_COMPAT is no longer needed. Temporary files are created in TMP, TEMP, or TMPDIR instead of c: tmp The installer is no more as it's not needed. There is a WinZip wrapped version for those with the extra bandwidth :). gbdk autodetects where it is installed - no more environment variables. cygwin1.dll and make are no longer required - gbdk is now compiled with mingw32.

See the ChangeLog section in the README for more information.

21st March, 2000
Problems with the installer. It seems that the demo of InstallVISE has an unreasonably short time limit. I had planed to use the demo until the license key came through, but there's no sign of the key yet and the 3 day evaluation is up. If anyone knows of a free Windows installer with the ability to modify environment variables, please contact me. I hear that temporarily setting you clock back to the 15th works...

18th March, 2000
libc5 version available / "Error creating temp file" Thanks to Rodrigo Couto there is now a Linux/libc5 version of gbdk3-2.92 available - follow the download link above. At least it will be there when the main sourceforge site comes back up... Also some people have reported a bug where the compiler reports '*** Error creating temp file'. Try typing "mkdir c: tmp" from a DOS prompt and see if that helps.

GBDK 2.92

8th March, 2000
Better than 2.91 :). Can now be installed anywhere. All the demos work. See the README for more.

  • All the examples now work (with a little bit of patching :)
    • Fixed problem with registers being cached instead of being marked volatile.
    • More register packing - should be a bit faster.
    • You can now install somewhere except c: gbdk | /usr/lib/gbdk
    • Arrays initialised with constant addresses a'la galaxy.c now work.
    • Fixed minor bug with 104$: labels in as.
    • Up to 167d/s...

GBDK 2.91

27th Feb, 2000
Better than 2.90 and includes Linux, win32 and a source tar ball. Some notes:

Read the README first Linux users need libgc-4 or above. Debian users try apt-get install libgc5. All the types have changed. Again, please read the README first. I prefer release early, release often. The idea is to get the bugs out there so that they can be squashed quickly. I've split up the libs so that they can be used on other platforms and so that the libs can be updated without updating the compiler. One side effect is that gb specific files have been shifted into their own directory i.e. gb.h is now gb/gb.h.

23rd Feb, 2000
First release of gbdk/sdcc. This is an early release - the only binary is for Linux and the source is only available through cvs. If your interested in the source, have a look at the cvs repository gbdk-support first, which will download all the rest of the code. Alternatively, look at gbdk-support and gbdk-lib at and sdcc at I will be working on binaries for Win32 and a source tar ball soon. Please report any bugs through the bugs link above.

31st Jan, 2000
Added Dermot's far pointer spec. It's mainly here for comment. If sdcc is ported to the Gameboy then I will be looking for some way to do far calls.

8th Jan, 2000
Moved over to Thanks must go to David Pfeffer for gbdk's previous resting place, The transition is not complete, but cvs and web have been shifted. Note that the cvs download instructions are stale - you should now look to I am currently working on porting sdcc over to the Z80. David Nathan is looking at porting it to the GB.

6th Jan, 2000
Icehawk wrote "I did write some rumble pack routines. Just make sure to remind people to add -Wl-yt0x1C or -Wl-yt0x1D or -Wl-yt0x1E depending on sram and battery usage. Find the routines on my site (as usual). =)"

18th Oct, 1999
Bug tracking / FAQ up. Try the link on the left to report any bugs with GBDK. It's also the first place to look if your having problems.

GBDK 2.1.5

17th Oct, 1999

The compiler is the same, but some of the libraries have been improved. memset() and memcpy() are much faster, malloc() is fixed, and a high speed fixed block alternative malloc() was added.