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python#10709: add back an updated AIX-NOTES (as README.AIX).
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This documentation tries to help people who intend to use Python on | ||
AIX. | ||
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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. | ||
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====================================================================== | ||
Compiling Python | ||
---------------------------------------------------------------------- | ||
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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. | ||
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Compiling with gcc: | ||
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cd Python-3.2 | ||
CC=gcc OPT="-O2" ./configure --enable-shared | ||
make | ||
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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. | ||
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It is a good idea to add the '-qmaxmem=70000' option, otherwise the | ||
compiler considers various files too complex to optimize. | ||
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Compiling with xlc: | ||
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cd Python-3.2 | ||
CC=xlc_r OPT="-O2 -qmaxmem=70000" ./configure --without-computed-gotos --enable-shared | ||
make | ||
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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. | ||
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====================================================================== | ||
Memory Limitations | ||
---------------------------------------------------------------------- | ||
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Note: this section may not apply when compiling Python as a 64 bit | ||
application. | ||
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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. | ||
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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. | ||
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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: | ||
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ldedit -b maxdata:0x20000000 ./python | ||
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You can allow up to 2GB of memory for Python by using the value | ||
0x80000000 for maxdata. | ||
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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. | ||
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http://publib.boulder.ibm.com/infocenter/aix/v6r1/index.jsp?topic=/com.ibm.aix.cmds/doc/aixcmds3/ldedit.htm | ||
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====================================================================== | ||
Known issues | ||
---------------------------------------------------------------------- | ||
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Those issues are currently affecting Python on AIX: | ||
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* Python has not been fully tested on AIX when compiled as a 64 bit | ||
application. | ||
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* 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 | ||
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* issue 11184: support for large files is currently broken | ||
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* issue 11185: os.wait4 does not behave correctly with option WNOHANG | ||
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* issue 1745108: there may be some problems with curses.panel | ||
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* issue 11192: test_socket fails | ||
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* issue 11190: test_locale fails | ||
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* issue 11193: test_subprocess fails | ||
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* issue 9920: minor arithmetic issues in cmath | ||
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* issue 11215: test_fileio fails | ||
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* issue 11188: test_time fails | ||
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====================================================================== | ||
Implementation details for developers | ||
---------------------------------------------------------------------- | ||
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Python and python modules can now be built as shared libraries on AIX | ||
as usual. | ||
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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. | ||
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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. | ||
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This mechanism should be transparent. |