Subject: HERE IS AIX-NOTES

From: Manus Hand <[email protected]>

To: Guido van Rossum <[email protected]>

Cc: [email protected]

Date: Thu, 8 Aug 1996 16:11:10 -0600 (MDT)

==============================================================================

COMPILER INFORMATION

------------------------------------------------------------------------------

(1) A problem has been reported with "make test" failing because of "weird

indentation." Searching the comp.lang.python newsgroup reveals several

threads on this subject, and it seems to be a compiler bug in an old

version of the AIX CC compiler. However, the compiler/OS combination

which has this problem is not identified. In preparation for the 1.4

release, Vladimir Marangozov ([email protected]) and Manus Hand

([email protected]) reported no such troubles for the following compilers and

operating system versions:

AIX C compiler version 3.1.2 on AIX 4.1.3 and AIX 4.1.4

AIX C compiler version 1.3.0 on AIX 3.2.5

If you have this problem, please report the compiler/OS version.

(2) Stefan Esser ([email protected]), in work done to compile Python

1.0.0 on AIX 3.2.4, reports that AIX compilers don't like the LANG

environment varaiable set to European locales. This makes the compiler

generate floating point constants using "," as the decimal seperator,

which the assembler doesn't understand (or perhaps it is the other way

around, with the assembler expecting, but not getting "," in float

numbers). "LANG=C; export LANG" solves the problem, as does

"LANG=C $(MAKE) ..." in the master Makefile.

(3) The cc (or xlc) compiler considers "Python/ceval.c" too complex to

optimize, except when invoked with "-qmaxmem=4000"

(4) Some problems (due to _AIX not being #defined) when python 1.0.0 was

compiled using 'gcc -ansi' were reported by Stefan Esser, but were not

investigated.

(5) The cc compiler has internal variables named "__abs" and "__div". These

names are reserved and may not be used as program variables in compiled

source. (As an anecdote in support of this, the implementation of

Python/operator.c had this problem in the 1.4 beta releases, and the

solution was to re#define some core-source variables having these names,

to give these python variables different names if the build is being done

on AIX.)

(6) As mentioned in the README, builds done immediately after previous builds

(without "make clean" or "make clobber") sometimes fail for mysterious

reasons. There are some unpredictable results when the configuration

is changed (that is, if you "configure" with different parameters) or if

intermediate changes are made to some files. Performing "make clean" or

"make clobber" resolves the problems.

==============================================================================

THREAD SUPPORT

------------------------------------------------------------------------------

AIX uses pthreads. However, as of AIX version 4, there are two (incompatible)

types of pthreads on AIX:

a) AIX DCE pthreads (on AIX 3.2.5)

b) AIX 4 pthreads (on AIX 4.1 and up)

Support has been added to Python to handle the distinction.

The cc and gcc compilers do not initialize pthreads properly. The only

compilers that can initialize pthreads properly are IBM *_r* compilers,

which use the crt0_r.o module, and which invoke ld with the reentrant

version of libc (libc_r).

In order to enable thread support, follow these steps:

1. Uncomment the thread module in Modules/Setup

2. configure --without-gcc --with-thread ...

3. make CC="cc_r" OPT="-O -qmaxmem=4000"

For example, to make with both threads and readline, use:

./configure --without-gcc --with-thread --with-readline=/usr/local/lib

make CC=cc_r OPT="-O2 -qmaxmem=4000"

If the "make" which is used ignores the "CC=cc_r" directive, one could alias

the cc command to cc_r (for example, in C-shell, perform an "alias cc cc_r").

Vladimir Marangozov ([email protected]) provided this information,

and he reports that a cc_r build initializes threads properly and that all

demos on threads run okay with cc_r.

==============================================================================

SHARED LIBRARY SUPPORT

------------------------------------------------------------------------------

AIX shared library support was added to Python in the 1.4 release by Manus

Hand ([email protected]) and Vladimir Marangozov ([email protected]).

Python modules may now be built as shared libraries on AIX using the normal

process of uncommenting the "*noconfig*" line in Modules/Setup.in before the

build. There is one additional step required, and that is to also uncomment

the line in Modules/Setup.in which reads

LINKCC= makexp_aix python.exp "" $(MYLIBS) $(ADDOBJS) ; $(CC)

AIX shared libraries require that an "export" and "import" file be provided

at compile time to list all extern symbols which may be shared between

modules. The effect of uncommenting the LINKCC line in Modules/Setup.in is

to create the "export" file for the modules and the libraries that belong to

the Python core. This is done by the "makexp_aix" script, which creates a

file named python.exp before performing the link of the python binary.

When shared library modules (.so files) are made, a second shell script

is invoked. This script is named "ld_so_aix" and is also provided with

the distribution in the Modules subdirectory. This script acts as an "ld"

wrapper which hides the explicit management of "export" and "import" files;

it adds the appropriate arguments (in the appropriate order) to the link

command that creates the shared module. Among other things, it specifies

that the "python.exp" file is an "import" file for the shared module.

A default python.exp file is provided with the distribution. It will be

overwritten (by the action of the makexp_aix script) if you build with shared

libraries. The python.exp file which comes with the distribution contains

all extern symbols of a completely statically build python executable.

Any python.exp file which is created from a build of python with some of the

modules linked as shared modules will obviously not list symbols from the now

dynamic modules. The distributed python.exp is provided so that, with

assistance from the ld_so_aix and makexp_aix scripts, shared extension

modules may be added to an otherwise completely static python build.

At the time of this writing, neither the python.exp file nor the makexp_aix

or ld_so_aix scripts are installed by the make procedure, so you should

remember to keep these and/or copy them to a different location for

safekeeping if you wish to use them to add shared extension modules to

python. However, if the make process has been updated since this writing,

these files MAY have been installed for you during the make by the

LIBAINSTALL rule, in which case the need to make safe copies is obviated.

If you wish to add a shared extension module to the language, you would follow

the steps given in the example below (the example adds the shared extension

module "spam" to python):

1. Make sure that "ld_so_aix" and "makexp_aix" are in your path.

2. The "python.exp" file should be in the current directory.

3. Issue the following commands or include them in your Makefile:

cc -c spammodule.c

ld_so_aix cc spammodule.o -o spammodule.so

For more detailed information on the shared library support, examine the

contents of the "ld_so_aix" and "makexp_aix" scripts or refer to the AIX

documentation.

==============================================================================