cpython/PC/os2emx/README.os2emx

This is a port of Python 2.3 to OS/2 using the EMX development tools
=========================================================================

What's new since the previous release
-------------------------------------

This release of the port incorporates the following changes from the 
December 24, 2001 release of the Python 2.2 port:

- based on the Python v2.3 final release source.
  

Licenses and info about Python and EMX
--------------------------------------

Please read the file README.Python-2.3 included in this package for 
information about Python 2.3.  This file is the README file from the 
Python 2.3 source distribution available via http://www.python.org/ 
and its mirrors.  The file LICENCE.Python-2.3 is the text of the Licence 
from the Python 2.3 source distribution.

Note that the EMX package that this package depends on is released under 
the GNU General Public Licence.  Please refer to the documentation 
accompanying the EMX Runtime libraries for more information about the 
implications of this.  A copy of version 2 of the GPL is included as the 
file COPYING.gpl2.

Readline and GDBM are covered by the GNU General Public Licence.  I think 
Eberhard Mattes' porting changes to BSD DB v1.85 are also GPL'ed (BSD DB 
itself is BSD Licenced).  ncurses and expat appear to be covered by MIT 
style licences - please refer to the source distributions for more detail.  
zlib is distributable under a very free license.  GNU MP and GNU UFC are 
under the GNU LGPL (see file COPYING.lib).

My patches to the Python-2.x source distributions, and any other packages 
used in this port, are placed in the public domain.

This software is provided 'as-is', without any express or implied warranty.
In no event will the author be held liable for any damages arising from the 
use of the software.

I do hope however that it proves useful to someone.


Other ports
-----------

There have been ports of previous versions of Python to OS/2.

The best known would be that by Jeff Rush, most recently of version 
1.5.2.  Jeff used IBM's Visual Age C++ (v3) for his ports, and his 
patches have been included in the Python 2.3 source distribution.

Andrew Zabolotny implemented a port of Python v1.5.2 using the EMX 
development tools.  His patches against the Python v1.5.2 source 
distribution have become the core of this port, and without his efforts 
this port wouldn't exist.  Andrew's port also appears to have been 
compiled with his port of gcc 2.95.2 to EMX, which I have but have 
chosen not to use for the binary distribution of this port (see item 21 
of the "YOU HAVE BEEN WARNED" section below).

Previous Python port releases by me:-
 - v2.0 on March 31, 2001;
 - v2.0 on April 25, 2001 (cleanup release + Stackless variant);
 - v2.1 on June 17, 2001;
 - v2.0 (Stackless re-release) on June 18, 2001.
 - v2.1.1 on August 5, 2001;
 - v2.1.1 on August 12, 2001 (cleanup release);
 - v2.1.1 (updated DLL) on August 14, 2001.
 - v2.2b2 on December 8, 2001 (not uploaded to archive sites)
 - v2.2c1 on December 16, 2001 (not uploaded to archive sites)
 - v2.2 on December 24, 2001

It is possible to have these earlier ports still usable after installing 
this port - see the README.os2emx.multiple_versions file, contributed by
Dr David Mertz, for a suggested approach to achieving this.


Software requirements
---------------------

This package requires the EMX Runtime package, available from the 
Hobbes (http://hobbes.nmsu.edu/) and LEO (http://archiv.leo.org/) 
archives of OS/2 software.  I have used EMX version 0.9d fix04 in 
developing this port.

My development system is running OS/2 v4 with fixpack 12.

3rd party software which has been linked into dynamically loaded modules:
- ncurses      (see http://dickey.his.com/ for more info, v5.2)
- GNU Readline (Kai Uwe Rommel's port available from Hobbes or LEO, v2.1)
- GNU GDBM     (Kai Uwe Rommel's port available from Hobbes or LEO, v1.7.3)
- zlib         (Hung-Chi Chu's port available from Hobbes or LEO, v1.1.3)
- expat        (from ftp://ftp.jclark.com/pub/xml/, v1.2)
- GNU MP       (Peter Meerwald's port available from LEO, v2.0.2)
- GNU UFC      (Kai Uwe Rommel's port available from LEO, v2.0.4)

The zlib module requires the Z.DLL to be installed - see the Installation 
section and item 12 of the "YOU HAVE BEEN WARNED" section for more 
information.

About this port
---------------

I have attempted to make this port as complete and functional as I can, 
notwithstanding the issues in the "YOU HAVE BEEN WARNED" section below.

Core components:

Python.exe is linked as an a.out executable, ie using EMX method E1 
to compile & link the executable.  This is so that fork() works (see 
"YOU HAVE BEEN WARNED" item 2).

Python23.dll is created as a normal OMF DLL, with an OMF import 
library and module definition file.  There is also an a.out (.a) import 
library to support linking the DLL to a.out executables.

This port has been built with complete support for multithreading.

Modules:

As far as possible, extension modules have been made dynamically loadable 
when the module is intended to be built this way.  I haven't yet changed 
the building of Python's standard modules over to using the DistUtils.

See "YOU HAVE BEEN WARNED" item 5 for notes about the fcntl module, and 
"YOU HAVE BEEN WARNED" item 14 for notes about the pwd and grp modules.

Support for case sensitive module import semantics has been added to match 
the Windows release.  This can be deactivated by setting the PYTHONCASEOK 
environment variable (the value doesn't matter) - see "YOU HAVE BEEN WARNED" 
item 16.

Optional modules:

Where I've been able to locate the required 3rd party packages already 
ported to OS/2, I've built and included them.

These include ncurses (_curses, _curses_panel), BSD DB (bsddb), 
GNU GDBM (gdbm, dbm), zlib (zlib), GNU Readline (readline), expat 
(pyexpat), GNU MP (mpz) and GNU UFC (crypt).

I have built these modules statically linked against the 3rd party 
libraries, with the exception of zlib.  Unfortunately my attempts to use 
the dll version of GNU readline have been a dismal failure, in that when 
the dynamically linked readline module is active other modules 
immediately provoke a core dump when imported.

Only the BSD DB package (part of the BSD package distributed with EMX) 
needed source modifications to be used for this port, pertaining to use 
of errno with multithreading.

The other packages, except for ncurses and zlib, needed Makefile changes 
for multithreading support but no source changes.

The _curses_panel module is a potential problem - see "YOU HAVE BEEN 
WARNED" item 17.

Upstream source patches:

No updates to the Python 2.3 release have become available.

Eberhard Mattes' EMXFIX04 update to his EMX 0.9d tools suite includes 
bug fixes for the BSD DB library.  The bsddb module included in this 
port incorporates these fixes.

Library and other distributed Python code:

The Python standard library lives in the Lib directory.  All the standard 
library code included with the Python 2.3 source distribution is included 
in the binary archive, with the exception of the dos-8x3 and tkinter 
subdirectories which have been omitted to reduce the size of the binary 
archive - the dos-8x3 components are unnecessary duplicates and Tkinter 
is not supported by this port (yet).  All the plat-* subdirectories in the 
source distribution have also been omitted, and a plat-os2emx directory 
included.

The Tools and Demo directories contain a collection of Python scripts.  
To reduce the size of the binary archive, the Demo/sgi, Demo/Tix, 
Demo/tkinter, Tools/audiopy and Tools/IDLE subdirectories have been 
omitted as not being supported by this port.  The Misc directory has 
also been omitted.

All subdirectories omitted from the binary archive can be reconstituted 
from the Python 2.3 source distribution, if desired.

Support for building Python extensions:

The Config subdirectory contains the files describing the configuration 
of the interpreter and the Makefile, import libraries for the Python DLL, 
and the module definition file used to create the Python DLL.  The 
Include subdirectory contains all the standard Python header files 
needed for building extensions.

As I don't have the Visual Age C++ compiler, I've made no attempt to 
have this port support extensions built with that compiler.


Packaging
---------

This port is packaged into several archives:
- python-2.3-os2emx-bin-02????.zip   (binaries, library modules)
- python-2.3-os2emx-src-03????.zip   (source patches and makefiles)

Documentation for the Python language, as well as the Python 2.3 
source distibution, can be obtained from the Python website 
(http://www.python.org/) or the Python project pages at Sourceforge 
(http://sf.net/projects/python/).


Installation
------------

Obtain and install, as per the included instructions, the EMX runtime 
package.

If you wish to use the zlib module, you will need to obtain and install 
the Z.DLL from Hung-Chi Chu's port of zlib v1.1.3 (zlib113.zip).  See also 
"YOU HAVE BEEN WARNED" item 12 below.

Unpack this archive, preserving the subdirectories, in the root directory 
of the drive where you want Python to live.

Add the Python directory (eg C:\Python23) to the PATH and LIBPATH 
variables in CONFIG.SYS.

You should then set the PYTHONHOME and PYTHONPATH environment variables 
in CONFIG.SYS.

PYTHONHOME should be set to Python's top level directory.  PYTHONPATH 
should be set to the semicolon separated list of principal Python library 
directories.
I use:
  SET PYTHONHOME=F:/Python23
  SET PYTHONPATH=F:/Python23/Lib;F:/Python23/Lib/plat-os2emx;
                 F:/Python23/Lib/lib-dynload;F:/Python23/Lib/site-packages

NOTE!:  the PYTHONPATH setting above is linewrapped for this document - it 
should all be on one line in CONFIG.SYS!

If you wish to use the curses module, you should set the TERM and TERMINFO 
environment variables appropriately.

If you don't already have ncurses installed, I have included a copy of the 
EMX subset of the Terminfo database included with the ncurses-5.2 source 
distribution.  This can be used by setting the TERMINFO environment variable 
to the path of the Terminfo subdirectory below the Python home directory.
On my system this looks like:
  SET TERMINFO=F:/Python23/Terminfo

For the TERM environment variable, I would try one of the following:
  SET TERM=ansi
  SET TERM=os2
  SET TERM=window

You will have to reboot your system for these changes to CONFIG.SYS to take 
effect.

If you wish to compile all the included Python library modules to bytecode, 
you can change into the Python home directory and run the COMPILEALL.CMD 
batch file.

You can execute the regression tests included with the Python 2.3 source 
distribution by changing to the Python 2.3 home directory and executing the 
REGRTEST.CMD batch file.  The following tests are known to fail at this 
time:
- test_longexp (see "YOU HAVE BEEN WARNED" item 1);
- test_mhlib (I don't know of any port of MH to OS/2);
- test_pwd (see "YOU HAVE BEEN WARNED" item 14, probably a bug in my code);
- test_grp (as per test_pwd);
- test_strftime (see "YOU HAVE BEEN WARNED" item 20);
- test_socketserver (fork() related, see "YOU HAVE BEEN WARNED" item 2).


YOU HAVE BEEN WARNED!!
----------------------

I know about a number of nasties in this port.

1.  EMX's malloc() and/or the underlying OS/2 VM system aren't particularly 
comfortable with Python's use of heap memory.  The test_longexp regression 
test exhausts the available swap space on a machine with 64MB of RAM with 
150MB of available swap space.

Using a crudely instrumented wrapper around malloc()/realloc()/free(), the 
heap memory usage of the expression at the core of the test 
(eval('[' + '2,' * NUMREPS + ']')) is as follows (approximately):
  NUMREPS = 1       => 300k
  NUMREPS = 10000   => 22MB
  NUMREPS = 20500   => 59MB

I don't even have enough memory to try for NUMREPS = 25000 :-(, let alone 
the NUMREPS = 65580 in test_longexp!  I do have a report that the test 
succeeds in the presence of sufficient memory (~200MB RAM).

During the course of running the test routine, the Python parser 
allocates lots of 21 byte memory chunks, each of which is actually 
a 64 byte allocation.  There are a smaller number of 3 byte allocations 
which consume 12 bytes each.  Consequently, more than 3 times as much 
memory is allocated than is actually used.

The Python Object Allocator code (PyMalloc) was introduced in Python 2.1 
for Python's core to be able to wrap the malloc() system to deal with 
problems with "unfriendly" malloc() behaviour, such as this.  Unfortunately 
for the OS/2 port, it is only supported for the allocation of memory for 
objects, whereas my research into this problem indicates it is the parser 
which is source of this particular malloc() frenzy.

I have attempted using PyMalloc to manage all of Python's memory 
allocation.  While this works fine (modulo the socket regression test 
failing in the absence of a socket.pyc), it is a significant performance 
hit - the time to run the regression test blows out from ~3.5 minutes to 
~5.75 minutes on my system.

I therefore don't plan to pursue this any further for the time being.

Be aware that certain types of expressions could well bring your system 
to its knees as a result of this issue.  I have modified the longexp test 
to report failure to highlight this.

2.  Eberhard Mattes, author of EMX, writes in his documentation that fork() 
is very inefficient in the OS/2 environment.  It also requires that the 
executable be linked in a.out format rather than OMF.  Use the os.exec 
and/or the os.spawn family of functions where possible.

{3.  Issue resolved...}

4.  In the absence of GNU Readline, terminating the interpreter requires a 
control-Z (^Z) followed by a carriage return.  Jeff Rush documented this 
problem in his Python 1.5.2 port.  With Readline, a control-D (^D) works 
as per the standard Unix environment.

5.  EMX only has a partial implementation of fcntl().  The fcntl module 
in this port supports what EMX supports.  If fcntl is important to you, 
please review the EMX C Library Reference (included in .INF format in the 
EMXVIEW.ZIP archive as part of the complete EMX development tools suite).
Because of other side-effects I have modified the test_fcntl.py test 
script to deactivate the exercising of the missing functionality.

6.  The BSD DB module is linked against DB v1.85.  This version is widely 
known to have bugs, although some patches have become available (and are 
incorporated into the included bsddb module).  Unless you have problems 
with software licenses which would rule out GDBM (and the dbm module 
because it is linked against the GDBM library) or need it for file format 
compatibility, you may be better off deleting it and relying on GDBM.  I 
haven't looked at porting the version of the module supporting the later 
SleepyCat releases of BSD DB, which would also require a port of the 
SleepyCat DB package.

7.  The readline module has been linked against ncurses rather than the 
termcap library supplied with EMX.

{8.  Workaround implemented}

9.  I have configured this port to use "/" as the preferred path separator 
character, rather than "\" ('\\'), in line with the convention supported 
by EMX.  Backslashes are still supported of course, and still appear in 
unexpected places due to outside sources that don't get normalised.

10. While the DistUtils components are now functional, other 
packaging/binary handling tools and utilities such as those included in
the Demo and Tools directories - freeze in particular - are unlikely to 
work.  If you do get them going, I'd like to know about your success.

11. I haven't set out to support the [BEGIN|END]LIBPATH functionality 
supported by one of the earlier ports (Rush's??).  If it works let me know.

12. There appear to be several versions of Z.DLL floating around - the one 
I have is 45061 bytes and dated January 22, 1999.  I have a report that 
another version causes SYS3175s when the zlib module is imported.

14. As a result of the limitations imposed by EMX's library routines, the 
standard extension module pwd only synthesises a simple passwd database, 
and the grp module cannot be supported at all.

I have written substitutes, in Python naturally, which can process real 
passwd and group files for those applications (such as MailMan) that 
require more than EMX emulates.  I have placed pwd.py and grp.py in 
Lib/plat-os2emx, which is usually before Lib/lib-dynload (which contains 
pwd.pyd) in the PYTHONPATH.  If you have become attached to what pwd.pyd 
supports, you can put Lib/lib-dynload before Lib/plat-os2emx in PYTHONPATH 
or delete/rename pwd.py & grp.py.

pwd.py & grp.py support locating their data files by looking in the 
environment for them in the following sequence:
pwd.py:  $ETC_PASSWD             (%ETC_PASSWD%)
         $ETC/passwd             (%ETC%/passwd)
         $PYTHONHOME/Etc/passwd  (%PYTHONHOME%/Etc/passwd)
grp.py:  $ETC_GROUP              (%ETC_GROUP%)
         $ETC/group              (%ETC%/group)
         $PYTHONHOME/Etc/group   (%PYTHONHOME%/Etc/group)

Both modules support using either the ":" character (Unix standard) or 
";" (OS/2, DOS, Windows standard) field separator character, and pwd.py 
implements the following drive letter conversions for the home_directory and 
shell fields (for the ":" separator only):
         $x  ->  x:
         x;  ->  x:

Example versions of passwd and group are in the Etc subdirectory.  Note 
that as of this release, this code fails the regression test.  I'm looking 
into why, and hope to have this fixed.

15. As of Python 2.1, termios support has mutated.  There is no longer a 
platform specific TERMIOS.py containing the symbolic constants - these 
now live in the termios module.  EMX's termios routines don't support all 
of the functionality now exposed by the termios module - refer to the EMX 
documentation to find out what is supported.

16. The case sensitive import semantics introduced in Python 2.1 for other 
case insensitive but case preserving file/operating systems (Windows etc), 
have been incorporated into this port, and are active by default.  Setting 
the PYTHONCASEOK environment variable (to any value) reverts to the 
previous (case insensitive) semantics.

17. Because I am statically linking ncurses, the _curses_panel 
module has potential problems arising from separate library data areas.
To avoid this, I have configured the _curses_.pyd (imported as 
"_curses_panel") to import the ncurses symbols it needs from _curses.pyd. 
As a result the _curses module must be imported before the _curses_panel 
module.  As far as I can tell, the modules in the curses package do this. 
If you have problems attempting to use the _curses_panel support please 
let me know, and I'll look into an alternative solution.

18. I tried enabling the Python Object Allocator (PYMALLOC) code.  While 
the port built this way passes the regression test, the Numpy extension 
(I tested v19.0.0) as built with with the port's DistUtils code doesn't 
work.  Specifically, attempting to "import Numeric" provokes a core dump.  
Supposedly Numpy v20.1.0 contains a fix for this, but for reason outlined 
in item 1 above, PYMALLOC is not enabled in this release.

19. sys.platform now reports "os2emx" instead of "os2".  os.name still 
reports "os2".  This change was to make it easier to distinguish between 
the VAC++ build (being maintained by Michael Muller) and the EMX build 
(this port), principally for DistUtils.

20. it appears that the %W substitution in the EMX strftime() routine has 
an off-by-one bug.  strftime was listed as passing the regression tests 
in previous releases, but this fact appears to have been an oversight in 
the regression test suite.  To fix this really requires a portable 
strftime routine - I'm looking into using one from FreeBSD, but its not 
ready yet.

21. previous releases of my Python ports have used the GCC optimisations 
"-O2 -fomit-frame-pointer".  After experimenting with various optimisation 
settings, including deactivating assert()ions, I have concluded that "-O2" 
appears the best compromise for GCC 2.8.1 on my hardware.  Curiously, 
deactivating assert() (via defining NDEBUG) _negatively_ impacts 
performance, allbeit only slightly, so I've chosen to leave the assert()s 
active.

I did try using Andrew Zabolotny's (p)gcc 2.95.2 compiler, and in 
general concluded that it produced larger objects that ran slower 
than Mattes' gcc 2.8.1 compiler.

Pystone ratings varied from just over 2000/s (no optimisation at all) 
to just under 3300/s (gcc 2.8.1, -O2) on my K6/2-300 system, for 
100,000 iterations per run (rather than the default 10000).

As a result of the optimisation change, the Python DLL is about 10% 
smaller than in the 2.1 release, and many of the dynamically loadable 
modules are smaller too.

[2001/08/12]

22.  As of this release, os.spawnv() and os.spawnve() now expose EMX's 
library routines rather than use the emulation in os.py.

In order to make use of some of the features this makes available in 
the OS/2 environment, you should peruse the relevant EMX documentation 
(EMXLIB.INF in the EMXVIEW.ZIP archive accompanying the EMX archives 
on Hobbes or LEO).  Be aware that I have exposed all the "mode" options 
supported by EMX, but there are combinations that either cannot be 
practically used by/in Python or have the potential to compromise your 
system's stability.

23.  pythonpm.exe in previous releases was just python.exe with the 
WINDOWAPI linker option set in the pythonpm.def file.  In practice, 
this turns out to do nothing useful.

I have written a replacement which wraps the Python DLL in a genuine 
Presentation Manager application.  This version actually runs the 
Python interpreter in a separate thread from the PM shell, in order 
that PythonPM has a functioning message queue as good PM apps should.
In its current state, PythonPM's window is hidden.  It can be displayed, 
although it will have no content as nothing is ever written to the 
window.  Only the "hide" button is available.  Although the code 
has support for shutting PythonPM down when the Python interpreter is 
still busy (via the "control" menu), this is not well tested and given 
comments I've come across in EMX documentation suggesting that the 
thread killing operation has problems I would suggest caution in 
relying on this capability.

PythonPM processes commandline parameters normally.  The standard input, 
output and error streams are only useful if redirected, as PythonPM's 
window is not a console in any form and so cannot accept or display 
anything.  This means that the -i option is ineffective.

Because the Python thread doesn't create its own message queue, creating 
PM Windows and performing most PM operations is not possible from within 
this thread.  How this will affect supporting PM extensions (such as 
Tkinter using a PM port of Tcl/Tk, or wxPython using the PM port of 
WxWindows) is still being researched.

Note that os.fork() _DOES_NOT_WORK_ in PythonPM - SYS3175s are the result 
of trying.  os.spawnv() _does_ work.  PythonPM passes all regression tests 
that the standard Python interpreter (python.exe) passes, with the exception 
of test_fork1 and test_socket which both attempt to use os.fork().

I very much want feedback on the performance, behaviour and utility of 
PythonPM.  I would like to add a PM console capability to it, but that 
will be a non-trivial effort.  I may be able to leverage the code in 
Illya Vaes' Tcl/Tk port, which would make it easier.

[2001/08/14]

24.  os.chdir() now uses EMX's _chdir2(), which supports changing 
both drive and directory at once.  Similarly, os.getcwd() now uses 
EMX's _getcwd() which returns drive as well as path.

[2001/12/08] - 2.2 Beta 2

25.  pyconfig.h (previously known as config.h) is now located in the 
Include subdirectory with all other include files.

[2001/12/16] - 2.2 Release Candidate 1

[2001/12/08] - 2.2 Final

... probably other issues that I've not encountered, or don't remember :-(

If you encounter other difficulties with this port, which can be 
characterised as peculiar to this port rather than to the Python release,
I would like to hear about them.  However I cannot promise to be able to do 
anything to resolve such problems.  See the Contact section below...


To do...
--------

In no particular order of apparent importance or likelihood...

- support Tkinter and/or alternative GUI (wxWindows??)


Credits
-------

In addition to people identified above, I'd like to thank:
- the BDFL, Guido van Rossum, and crew for Python;
- Dr David Mertz, for trying out a pre-release of this port;
- the Python-list/comp.lang.python community;
- John Poltorak, for input about pwd/grp.

Contact
-------

Constructive feedback, negative or positive, about this port is welcome 
and should be addressed to me at the e-mail addresses below.

I intend creating a private mailing list for announcements of fixes & 
updates to this port.  If you wish to receive such e-mail announcments, 
please send me an e-mail requesting that you be added to this list.

Andrew MacIntyre
E-mail: andymac@bullseye.apana.org.au, or andymac@pcug.org.au
Web:    http://www.andymac.org/

24 December, 2001.