a gcc-based cross-compiler for classic 68K and PPC Macintoshes
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A GCC-based cross-compilation environment for 68K Macs. Why? Because there is no decent C++11 Compiler targetting Apple's System 6. If that's not a sufficient reason for you, I'm sure you will find someting more useful elsewhere.

If you are crazy enough to try it out, please say hello at wolfgang.thaller@gmx.net.


  • Linux or Mac OS X
  • boost, if using gcc 4.8 or earlier to compile on Linux
  • CMake 2.8
  • GCC dependencies: GMP 4.2+, MPFR 2.3.1+ and MPC 0.8.0+
  • Apple Universal Interfaces (tested with version 3.1 - see below)
  • An ancient Mac and/or an emulator.

For Ubuntu Linux, the following should help a bit:

sudo apt-get install cmake libgmp-dev libmpfr-dev libmpc-dev

On a Mac, get the homebrew package manager and:

brew install cmake gmp mpfr libmpc

Apple Universal Interfaces

The Universal Interfaces used to be a free download from Apple. However, they have taken the site offline and the license agreement prohibits redistribution, so this might be a bit hard to find nowadays.

You do need a version that still supports 68K Mac development.

The package might be somewhere in this huge snapshot of Apple's FTP site made by the Internet Archive: https://archive.org/details/ftpsites_developer.apple.com

If you have a Mac or some other way to read DiskCopy images, grab the MPW 3.5 image from:


and use the CIncludes directory from there.

Put the C header files into a directory called "CIncludes" at the top level of the Retro68 directory.


Once you have all the prerequisites, execute these commands from the top level of the Retro68 directory:

cd ..
mkdir Retro68-build
cd Retro68-build
sh ../Retro68/build-toolchain.sh 

The toolchain will be installed in the "toolchain" directory inside the build directory.

Sample programs

Sample programs are built as MacBinary files (.bin) and also automatically wrapped into raw disk images (.dsk). Look under Retro68-build/build-target/ for the compiled binaries.


Retro68 is an aggegation of various existing free software projects with a few small key components added.

Third Party Components:

  • binutils 2.20.1
  • gcc 4.9.1 with some Retro68-specific hacks
  • newlib 2.10.1 (inside the gcc directory)
  • elf2flt (from the ucLinux project's CVS)
  • hfsutils 3.2.6 (just for convenience)

Retro68-Specific Components:

  • ASFilter
  • PrepareHeaders.hs
  • MakeAPPL
  • libretro
  • Sample Program: Raytracer
  • Sample Program: App2


Currently unmodified from the original. Configured for m68k-unknown-elf.


Various patches and hacks, most importantly:

  • Changed register usage.
  • Change the way 1-byte and 2-byte parameters are passed.
  • support `"\pPascal String Literals"``
  • added a pascal calling convention (pascal or __attribute__((__pascal__)))
  • added __attribute__((__raw_inline__(word1, word2, word3))) to emulate ONEWORDINLINE and friends
  • added __attribute__((regparam("..."))) to specify custom register calling conventions
    • added #pragma parameter to specify custom register calling conventions


Standard C library. Currently unmodified. The missing platform-dependent bits haven't been added, instead they are found in 'libretro'.


Converts from ELF to a much simpler binary format. Minor patch: provide symbols around .init and .fini sections


Included for convenience. No changes.


Apply any necessary patches to Apple's headers; currently, this only modifies ConditionalMacros.h.


An evil hack. Installs a replacement for m68k-unknown-elf-as that runs a few regexps on generated assembly code. Two things are changed:

  1. Replace occurrences of the RTD instruction, with something that is supported on 68000 as well. GCC currently generates this in pascal functions that you declare.
  2. While we're at it, remove unnecessary duplicate RTS instructions from MacsBug symbol names.


Reads a FLAT executable as output by elf2flt and converts it to a MacBinary file containing a classic Macintosh application.


Contains startup code (handles relocations) and implementations for some standard library functions.

Sample Program: App2

Simple test program, includes an implementation of a simple text console window.

The binary is at Retro68-build/build-target/App2/Test.bin in MacBinary format and also on a disk image named Test.dsk.

Sample Program: Raytracer

Calculates a nice 3D image, pixel by pixel. There are two versions: raytracer.c is a straightforward plain C implementation using floating point arithmetic.

Raytracer2 makes use of C++ features; it also uses fixed point arithmetic instead of floating point (operator overloading FTW).

The binaries are in Retro68-build/build-target/Raytracer. Both MacBinary (.bin) and disk image (.dsk) formats are built.


The original parts of Retro68 are licensed under GPL3+, as are most other parts. Some parts are licensed GPL2+ or with more liberal licenses. Check the copyright notices in the individual files.