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1
2This documentation tries to help people who intend to use Python on
3AIX.
4
5There used to be many issues with Python on AIX, but the major ones
6have been corrected for version 3.2, so that Python should now work
7rather well on this platform. The remaining known issues are listed in
8this document.
9
10
11======================================================================
12			   Compiling Python
13----------------------------------------------------------------------
14
15You can compile Python with gcc or the native AIX compiler. The native
16compiler used to give better performances on this system with older
17versions of Python.  With Python 3.2 it may not be the case anymore,
18as this compiler does not allow compiling Python with computed gotos.
19Some benchmarks need to be done.
20
21Compiling with gcc:
22
23cd Python-3.2
24CC=gcc OPT="-O2" ./configure --enable-shared
25make
26
27There are various aliases for the native compiler.  The recommended
28alias for compiling Python is 'xlc_r', which provides a better level of
29compatibility and handles thread initialization properly.
30
31It is a good idea to add the '-qmaxmem=70000' option, otherwise the
32compiler considers various files too complex to optimize.
33
34Compiling with xlc:
35
36cd Python-3.2
37CC=xlc_r OPT="-O2 -qmaxmem=70000" ./configure --without-computed-gotos --enable-shared
38make
39
40
41======================================================================
42			  Memory Limitations
43----------------------------------------------------------------------
44
45Note: this section may not apply when compiling Python as a 64 bit
46application.
47
48By default on AIX each program gets one segment register for its data
49segment. As each segment register covers 256 MiB, a Python program that
50would use more than 256 MiB will raise a MemoryError.  The standard
51Python test suite is one such application.
52
53To allocate more segment registers to Python, you must use the linker
54option -bmaxdata or the ldedit tool to specify the number of bytes you
55need in the data segment.
56
57For example, if you want to allow 512 MiB of memory for Python (this is
58enough for the test suite to run without MemoryErrors), you should run
59the following command at the end of compilation:
60
61ldedit -b maxdata:0x20000000 ./python
62
63You can allow up to 2 GiB of memory for Python by using the value
640x80000000 for maxdata.
65
66It is also possible to go beyond 2 GiB of memory by activating Large
67Page Use. You should consult the IBM documentation if you need to use
68this option. You can also follow the discussion of this problem
69in issue 11212 at bugs.python.org.
70
71http://publib.boulder.ibm.com/infocenter/aix/v6r1/index.jsp?topic=/com.ibm.aix.cmds/doc/aixcmds3/ldedit.htm
72
73
74======================================================================
75			     Known issues
76----------------------------------------------------------------------
77
78Those issues are currently affecting Python on AIX:
79
80* Python has not been fully tested on AIX when compiled as a 64 bit
81  application.
82
83* issue 3526: the memory used by a Python process will never be
84  released to the system. If you have a Python application on AIX that
85  uses a lot of memory, you should read this issue and you may
86  consider using the provided patch that implements a custom malloc
87  implementation
88
89* issue 11192: test_socket fails
90
91* issue 11190: test_locale fails
92
93* issue 11193: test_subprocess fails
94
95* issue 9920: minor arithmetic issues in cmath
96
97* issue 11215: test_fileio fails
98
99
100
101======================================================================
102		Implementation details for developers
103----------------------------------------------------------------------
104
105Python and python modules can now be built as shared libraries on AIX
106as usual.
107
108AIX shared libraries require that an "export" and "import" file be
109provided at compile time to list all extern symbols which may be
110shared between modules.  The "export" file (named python.exp) for the
111modules and the libraries that belong to the Python core is created by
112the "makexp_aix" script before performing the link of the python
113binary. It lists all global symbols (exported during the link) of the
114modules and the libraries that make up the python executable.
115
116When shared library modules (.so files) are made, a second shell
117script is invoked.  This script is named "ld_so_aix" and is also
118provided with the distribution in the Modules subdirectory.  This
119script acts as an "ld" wrapper which hides the explicit management of
120"export" and "import" files; it adds the appropriate arguments (in the
121appropriate order) to the link command that creates the shared module.
122Among other things, it specifies that the "python.exp" file is an
123"import" file for the shared module.
124
125This mechanism should be transparent.
126