# Building Mac Python from source

This document explains how to build MacPython from source. This is necessary if you want to make modifications to the Python core. Building Python is not something to be undertaken lightly, you need a reasonable working knowledge of the CodeWarrior development environment, a good net connection and probably quite some time too.

The information density in this file is high, so you should probably print it and read it at your leasure. Most things are explained only once (and probably in the wrong place:-).

> First a warning: this information may become outdated if a new CodeWarrior is released after MacPython. The MacPython homepage will hopefully have updated instructions in that case.

I am very interested in feedback on this document, send your comments to the Mac Python Special Interest Group.

## What you need.

The following things you definitely need:

- You need a MacPython source distribution, of course. You can obtain one via http://www.cwi.nl/~jack/macpython.html (which has up-to-date links to the other packages needed too) and possibly also from the standard python.org ftp site.
  A better alternative is to check the sources straight out of the CVS repository, see below. Most of the packages mentioned here are also available through CVS. Check the section on CVS repository use below.
- You need MetroWerks CodeWarrior. The current distribution has been built with CodeWarrior Pro 6.1. Ordering information is available on the MetroWerks homepage. Building Python with MPW, Think/Symantec C or the OSX developer tools is impossible without major surgery.
- You need GUSI version 2, the Grand Unified Socket Interface, by Matthias Neeracher. The original GUSI is obtainable from ftp://gusi.sourceforge.net/pub/gusi/. At the moment Python is built with a slightly modified version of GUSI 2.1.1, so it may be better to check the MacPython homepage for a GUSI that is most easily used for building Python.

The MacPython project files are configured to include a plethora of optional modules, and these modules need a number of extra packages. To use the project files as-is you have to download these packages too. Python has all such modules as dynamically loaded modules, so if you don't need a certain package it suffices to just refrain from builing the extension module. Here are the locations for the various things you need:

- Tcl and Tk are in a sad state on the Mac, the standard source distributions simply don't compile, so I have created a distribution especially for use with MacPython. See the section on building Tcl/Tk Python below.
- Waste, a TextEdit replacement written by Marco Piovanelli, <piovanel@kagi.com>. Python was built using version 2.0, which is included in the CodeWarrior package. You can also obtain it from <http://www.merzwaren.com/waste> and various other places.
- Gdbm library for the Mac. Available from Jack's Mac software page at http://www.cwi.nl/~jack/macsoftware.html and ftp://ftp.cwi.nl/pub/jack/mac.
- JPEG library by the Independent JPEG Group. A version including Mac projects can be found at Jack's page mentioned above. The most recent JPEG library can always be obtained from ftp://ftp.uu.net/graphics/jpeg/.
- The netpbm/pbmplus, libtiff, zlib and png libraries. The netpbm distribution (which includes libtiff) is generally available on Internet ftp servers. For Python pbmplus, an older incarnation of netpbm, is functionally identical to netpbm, since Python only uses the library and not the complete applications. A distribution with correct projects and library source only is available from, you guessed it, Jack's Mac software page mentioned above.

## Setting Up

Now that you have collected everything you should start with building the various parts. If you don't want to fix access paths try to set things up as follows:

    Top-level-folder:
    	GUSI2
    	GUSI2Carbon
    	imglibs
    		jpeg
    		netpbm
    			libtiff
    		zlib
    		png
    	gdbm
    	Python
    		Modules
    		...
    		Mac
    			Modules
    			Build
    			...
    	Tcl/Tk Folder
    		tcl8.0
    		tk8.0
    		MoreFiles 1.4.3

If your setup of the libraries is exactly the same as mine (which is not very likely, unless you happen to work from the same CVS repository) you can use the project `buildlibs.prj` in the `:Mac:Build` folder to build all needed libraries in one fell swoop, otherwise you will have to build the libraries one by one.

First build GUSI, both the norla one and the Carbon variant.

Next, in `libjpeg`, `pbmplus`, `zlib`, `libpng`, `gdbm`, and`libtiff` you build all projects. Usually the projects are in "mac" subfolders, sometimes they are in the main folder. Tcl/tk is a special case, see below.

## Building Tcl/Tk

The Tcl/Tk 8.3.0 source distribution does not work on the Mac. I have created an archive of the sources that I used to build _tkinter for MacPython, you can obtain this from ftp://ftp.cwi.nl/pub/jack/python/mac/tcltk830src-for-python.sit. Only the libraries needed to build _tkinter for PPC have been fixed.

Note that if you use a different release of Tcl and Tk than the ones I have used you may have to adapt the Python `tkresources.rsrc` file. This is easiest done by building `SimpleTk` and copying the TEXT, ICON and CRSR resources from it to `tkresources.rsrc`. This allows the `_tkinter` module to work without an installed Tk/Tcl on your machine.

Also note that the `_tkinter.ppc.slb` that is normally distributed in the `PlugIns` folder is the one from the Imaging extension, which has some extra features needed by PIL (and which features should not hinder normal operation). Build first the Tcl library, then SimpleTcl (test it by typing `ls -l` in the window you get) then the Tk library, then SimpleTk (which can again be tested with `ls -l`). If this all worked you are all set to try building Python.

## Building Waste

You do not need to build the Waste libraries, as Python includes the source modules themselves.

## The organization of the Python source tree

Time for a short break, while we have a look at the organization of the Python source tree. At the top level, we find the following folders:

Demo
  Demo programs that are not Mac-specific. Some of these may not work.
Extensions
  Extensions to the interpreter that are not Mac-specific. Contains the `img`, `Imaging` and `Numerical` extensions in this distribution.
Grammar
  The Python grammar. Included for reference only, you cannot build the parser on a Mac.
Include
  Machine-independent header files.
Modules
  Machine-independent optional modules. Not all of these will work on the Mac.
Objects
  Machine-independent code for various object types. Most of these are not really optional: the interpreter will not function without them.
Parser
  The Python parser (machine-independent).
Python
  The core interpreter. Most files are machine-independent, some are unix-specific and not used on the Mac.
Tools
  Tools for python developers. Contains `modulator` which builds skeleton C extension modules, `bgen` which generates complete interface modules from information in C header files and `freeze` which is used to turn Python scripts into real applications (used by MacFreeze and BuildApplication) There are some readme files, but more documentation is sorely needed.

All the mac-specific stuff lives in the `Mac` folder:

Build
  This is where the project files live and where you build the libraries, shared libraries, executables and plugin modules. All the resulting binaries, except for intermedeate results, are deposited in the toplevel folder or the Mac:PlugIns folder (for plugin modules).
Compat
  Unix-compatability routines. Most of these are not used anymore, since GUSI provides a rather complete emulation, but you may need these if you are trying to build a non-GUSI python.
Demo
  Mac-specific demo programs, some of them annotated.
Include
  Mac-specific but compiler-independent include files.
Lib
  Mac-specific standard modules. The `toolbox` folder contains modules specifically needed with various MacOS toolbox interface modules.
Modules
  Mac-specific builtin modules. Theoretically these are all optional, but some are rather essential (like `macosmodule`). A lot of these modules are generated with `bgen`, in which case the bgen input files are included so you can attempt to regenerate them or extend them.
MPW
  MPW-specific files. These have not been used or kept up-to-date for a long time, so use at your own risk.
mwerks
  Mwerks-specific sources and headers. Contains glue code for Pythons shared-library architecture, a replacement for `malloc` and a directory with various projects for building variations on the Python interpreter. The `mwerks_*.h` files here are the option-setting files for the various interpreters and such, comparable to the unix command-line `-D` options to the compiler. Each project uses the correct option file as its "prefix file" in the "C/C++ language" settings. Disabling optional modules (for the 68K interpreter), building non-GUSI interpreters and various other things are accomplished by modifying these files (and possibly changing the list of files included in the project window, of course).
PlugIns
  This is where the Classic and Carbon dynamically-loaded plugin modules live.
Python
  Mac-specific parts of the core interpreter.
Resources
  Resource files needed to build the interpreter.
Scripts
  A collection of various mac-specific Python scripts. Some are essential, some are useful but few are documented, so you will have to use your imagination to work them out.
Tools
  A collection of tools, usually bigger than those in the scripts folder. The important ones here are the IDE and macfreeze. The IDE is built with the buildIDE.py script, which puts the resulting applet in the toplevel folder. Macfreeze is usually invoked through the BuildApplication script, but for more control over the freezing process you can run the main script here.
Unsupported
  Modules that are not supported any longer but may still work with a little effort.

## Building the PPC interpreter

This is different under 2.1. You are best off using the fullbuild.py script, see below.

First you optionally build the external libraries with buildlibs.prj. Next, the projects for interpreter and core library are linked together, so building the PythonInterpreterClassic and/or PythonInterpreterCarbon target in `PythonInterpreter.prj` will result in everything being built. The result, however, is an "Application template", (filetype Atmp). If you don't use fullbuild you can manually turn either of these into an interpreter by copying it to PythonInterpreter and setting the filetype to APPL (with ResEdit or some such).

Fullbuild does this for you, and the Atmp files is also how ConfigurePythonCarbon and ConfigurePythonClassic work their magic.

For completeness sake here is a breakdown of the projects:

PythonCore
  The shared library that contains the bulk of the interpreter and its resources. It has targets for PythonCore and PythonCoreCarbon. It is a good idea to immedeately put an alias to this shared library in the `Extensions` folder of your system folder. Do exactly that: put an alias there, copying or moving the file will cause you grief later if you rebuild the library and forget to copy it to the extensions folder again. The ConfigurePythonXXX applets will also do this.
PythonInterpeter
  The interpreter. This is basically a routine to call out to the shared library. Unlike in previous releases the same program is used for creating applets (for which formerly PythonApplet was used).

Plugin projects
  Each plugin module has a separate project, and these can be rebuilt on the fly. Fullbuild (or actually it's little helper genpluginprojects) takes care of this.

After creating the alias to `PythonCore` you remove any old `Python XXXX Preferences` file from the `Preferences` folder (if you had python installed on your system before) and run the interpreter once to create the correct preferences file.

Next, you have to build the extension modules. If you don't use fullbuild simply open each project and build it.

Finally, you must build the standard applets: `EditPythonPrefs`, `BuildApplet`, etc. For the N-th time: fullbuild does this for you, but you can also manually drag/drop them onto BuildApplet.

> The `fullbuild` script can be used to build everything, but you need a fully-functional interpreter before you can use it (and one that isn't rebuilt in the process: you cannot rebuild a running program). You could copy the interpreter to a different place and use that to run fullbuild. The `PythonStandSmall.prj` project builds an interpreter that is suited to this, and it can also come in handy if you need to debug things (which is easier in a static program).

You are all set now, and should read the release notes and `ReadMe` file from the `Mac` folder.

## Rebuilding `.exp` files

Occasionally it may be necessary to rebuild your PythonCore `.exp` file, a file that controls which symbols are exported by your PythonCore shared library. Rebuild it if you get unexpected undefined symbols when you are building a plugin module.

Rebuilding the .exp file is done by first both removing the file and removing the reference to it in the project (in the "config" section). Next, build PythonCore or PythonCoreCarbon. This will create a new .exp file, with the name `PythonCore.mcp.exp`. Rename this file to either `PythonCore.exp` or `PythonCoreCarbon.exp` and add this file back to the project. Next, edit ot to remove the references to the symbols `__initialize`, `__terminate`, `setjmp`, `longjmp`, `vec_longjmp`, `main` and `__ptmf_null`. They are all close together about halfway the file. Finally rebuild again.

This rather convoluted procedure is needed to ensure that plugin modules don't accidentally link with those entrypoints from PythonCore, which will not work because those routines have to be in the same code fragment as they are used from.

## Using the CVS source archive

It is possible (and probably best) to access the Python sources through remote CVS. The advantage of this is that you get the very latest sources, so any bug fixed or new features will be immedeately available. This is also the disadvantage, of course: as this is the same tree as is used for development it may sometimes be a little less stable.

The CVS client of choice is Alexandre Parenteau's MacCVS. It can be obtained through the WinCVS homepage. MacCVS uses Internet Config to set file types correctly based on the filename extension. In the maccvs preferences you should also set (in the "binary files" section) "use mac encoding: applesingle" and (in the "text files" section) "use ISO latin 1 conversion".

> There is one group of people for whom MacCVS is not the best choice: people with checkin rights to the Python repository. You will have to use MacCVS Pro (completely unrelated) from www.maccvs.org, because it has working SSH support.

It is a good idea to disable Quicktime Exchange in the Quicktime control panel. Quicktime Exchange will magically map some extensions to filetypes, and this can seriously hinder you if, for instance, `.bmp` is not a Windows bitmap file.

The Python sources are checked out from the main Python CVS archive on sourceforge.net, see the Source access via CVS page for details. When you check the sources out you will get something like `Python:dist:src`, and under that the `Modules`, `Lib`, `Mac` etc hierarchy. The `src` folder can be renamed to `Python`, and is what this document refers to as the "toplevel Python folder".

The CVS repository does not contain all the projects for the plugin modules, these are built with `fullbuild.py` normally. For this reason it is probably a good idea to first build `PythonStandSmall.prj`, which builds a fairly minimal interpreter, and then follow the fullbuild instructions.

## Odds and ends

Some remarks that I could not fit in elsewhere:

- It may be possible to use the `PythonCore` shared library to embed Python in another program, if your program can live with using GUSI for I/O. Use PythonCore in stead of your MSL C library (or, at the very least, link it before the normal C library).
- It is possible to build PPC extension modules without building a complete Python. The binary distribution installer can optionally install all the needed folders (the develop option). A template for a dynamic module can be found in `xx.prj`.
- The Python shared library architecture is a variant of the architecture described as "application with shared libraries and dropins" in the MetroWerks "Targeting MacOS" documentation. The Python Application and applet-template use the `MSL AppRuntime.Lib` runtime library (with properly set CFM initialization and termination routines). PythonCore uses `MSL Runtime.Lib`, which is really intended for standalone programs but which we fool into working by providing a dummy main program. It is linked statically into PythonCore (and exported to the applications and plugins) so we do not have to distribute yet another shared library. Plugin modules use `MSL ShlibRuntime.Lib` (not the dropin runtime: modules are never unloaded) and obtain the rest from PythonCore. PythonCore uses a non-standard initialization entry point, `__initialize_with_resources`, to be able to obtain resources from the library file later on. Plugins can do the same (_tkinter does) or use the standard `__initialize` entry point.