Misc/README.AIX - platform/external/python - Git at Google


 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.

	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.