This documentation tries to help people who intend to use Python on AIX. There used to be many issues with Python on AIX, but the major ones have been corrected for version 3.2, so that Python should now work rather well on this platform. The remaining known issues are listed in this document. ====================================================================== Compiling Python ---------------------------------------------------------------------- You can compile Python with gcc or the native AIX compiler. The native compiler used to give better performances on this system with older versions of Python. With Python 3.2 it may not be the case anymore, as this compiler does not allow compiling Python with computed gotos. Some benchmarks need to be done. Compiling with gcc: cd Python-3.2 CC=gcc OPT="-O2" ./configure --enable-shared make There are various aliases for the native compiler. The recommended alias for compiling Python is 'xlc_r', which provides a better level of compatibility and handles thread initialization properly. It is a good idea to add the '-qmaxmem=70000' option, otherwise the compiler considers various files too complex to optimize. Compiling with xlc: cd Python-3.2 CC=xlc_r OPT="-O2 -qmaxmem=70000" ./configure --without-computed-gotos --enable-shared make Note: On AIX 5.3 and earlier, you will also need to specify the "--disable-ipv6" flag to configure. This has been corrected in AIX 6.1. ====================================================================== Memory Limitations ---------------------------------------------------------------------- Note: this section may not apply when compiling Python as a 64 bit application. By default on AIX each program gets one segment register for its data segment. As each segment register covers 256 MB, a Python program that would use more than 256MB will raise a MemoryError. The standard Python test suite is one such application. To allocate more segment registers to Python, you must use the linker option -bmaxdata or the ldedit tool to specify the number of bytes you need in the data segment. For example, if you want to allow 512MB of memory for Python (this is enough for the test suite to run without MemoryErrors), you should run the following command at the end of compilation: ldedit -b maxdata:0x20000000 ./python You can allow up to 2GB of memory for Python by using the value 0x80000000 for maxdata. It is also possible to go beyond 2GB of memory by activating Large Page Use. You should consult the IBM documentation if you need to use this option. You can also follow the discussion of this problem in issue 11212 at bugs.python.org. http://publib.boulder.ibm.com/infocenter/aix/v6r1/index.jsp?topic=/com.ibm.aix.cmds/doc/aixcmds3/ldedit.htm ====================================================================== Known issues ---------------------------------------------------------------------- Those issues are currently affecting Python on AIX: * Python has not been fully tested on AIX when compiled as a 64 bit application. * issue 3526: the memory used by a Python process will never be released to the system. If you have a Python application on AIX that uses a lot of memory, you should read this issue and you may consider using the provided patch that implements a custom malloc implementation * issue 11184: support for large files is currently broken * issue 11185: os.wait4 does not behave correctly with option WNOHANG * issue 1745108: there may be some problems with curses.panel * issue 11192: test_socket fails * issue 11190: test_locale fails * issue 11193: test_subprocess fails * issue 9920: minor arithmetic issues in cmath * issue 11215: test_fileio fails * issue 11188: test_time fails ====================================================================== Implementation details for developers ---------------------------------------------------------------------- Python and python modules can now be built as shared libraries on AIX as usual. 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 "export" file (named python.exp) for the modules and the libraries that belong to the Python core is created by the "makexp_aix" script before performing the link of the python binary. It lists all global symbols (exported during the link) of the modules and the libraries that make up the python executable. 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. This mechanism should be transparent.