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
40Note:
41On AIX 5.3 and earlier, you will also need to specify the
42"--disable-ipv6" flag to configure. This has been corrected in AIX
436.1.
44
45
46======================================================================
47			  Memory Limitations
48----------------------------------------------------------------------
49
50Note: this section may not apply when compiling Python as a 64 bit
51application.
52
53By default on AIX each program gets one segment register for its data
54segment. As each segment register covers 256 MB, a Python program that
55would use more than 256MB will raise a MemoryError.  The standard
56Python test suite is one such application.
57
58To allocate more segment registers to Python, you must use the linker
59option -bmaxdata or the ldedit tool to specify the number of bytes you
60need in the data segment.
61
62For example, if you want to allow 512MB of memory for Python (this is
63enough for the test suite to run without MemoryErrors), you should run
64the following command at the end of compilation:
65
66ldedit -b maxdata:0x20000000 ./python
67
68You can allow up to 2GB of memory for Python by using the value
690x80000000 for maxdata.
70
71It is also possible to go beyond 2GB of memory by activating Large
72Page Use. You should consult the IBM documentation if you need to use
73this option. You can also follow the discussion of this problem
74in issue 11212 at bugs.python.org.
75
76http://publib.boulder.ibm.com/infocenter/aix/v6r1/index.jsp?topic=/com.ibm.aix.cmds/doc/aixcmds3/ldedit.htm
77
78
79======================================================================
80			     Known issues
81----------------------------------------------------------------------
82
83Those issues are currently affecting Python on AIX:
84
85* Python has not been fully tested on AIX when compiled as a 64 bit
86  application.
87
88* issue 3526: the memory used by a Python process will never be
89  released to the system. If you have a Python application on AIX that
90  uses a lot of memory, you should read this issue and you may
91  consider using the provided patch that implements a custom malloc
92  implementation
93
94* issue 11184: support for large files is currently broken
95
96* issue 11185: os.wait4 does not behave correctly with option WNOHANG
97
98* issue 1745108: there may be some problems with curses.panel
99
100* issue 11192: test_socket fails
101
102* issue 11190: test_locale fails
103
104* issue 11193: test_subprocess fails
105
106* issue 9920: minor arithmetic issues in cmath
107
108* issue 11215: test_fileio fails
109
110* issue 11188: test_time fails
111
112
113======================================================================
114		Implementation details for developers
115----------------------------------------------------------------------
116
117Python and python modules can now be built as shared libraries on AIX
118as usual.
119
120AIX shared libraries require that an "export" and "import" file be
121provided at compile time to list all extern symbols which may be
122shared between modules.  The "export" file (named python.exp) for the
123modules and the libraries that belong to the Python core is created by
124the "makexp_aix" script before performing the link of the python
125binary. It lists all global symbols (exported during the link) of the
126modules and the libraries that make up the python executable.
127
128When shared library modules (.so files) are made, a second shell
129script is invoked.  This script is named "ld_so_aix" and is also
130provided with the distribution in the Modules subdirectory.  This
131script acts as an "ld" wrapper which hides the explicit management of
132"export" and "import" files; it adds the appropriate arguments (in the
133appropriate order) to the link command that creates the shared module.
134Among other things, it specifies that the "python.exp" file is an
135"import" file for the shared module.
136
137This mechanism should be transparent.
138