SWIG problems - "ImportError: dynamic module does not define......."

Discussion in 'Python' started by Chris Hodapp, Dec 16, 2003.

  1. Chris Hodapp

    Chris Hodapp Guest

    I have seen messages posted about this before, and there is a clear
    reference to it in the manual, but I have been unable to find a
    solution.

    I'm on Slackware 9.1, kernel 2.6.0-test11, using Python 2.3.1 and
    GCC 3.2.3 (both installed by default with Slackware) and SWIG 1.3.19,
    compiled from source code.
    I messed around a little on my own and couldn't get things to work
    right,
    so I copied the examples from the book, nearly verbatim but with some
    minor changes to fit my configuration.

    I copied the example code exactly into example.i and example.c, and
    did
    the following commands:
    swig -python example.i
    gcc -c example.c example_wrap.c -I/usr/include/python2.3
    ld -shared example.o example_wrap.o -o _example.so
    .... and several other times in the last command I tried some other
    things like examplemodule.so and example.so. All of these worked
    without
    error, so I tried it from within Python, and got the usual error about
    "ImportError: dynamic module does not define init function" when I
    tried
    'import example'. It made no difference if I added the path with all
    the
    files to sys.path; the same error occurred.

    I tried this several times over, and I could never get it to work
    right. The last helpful suggestion I saw on here was that I did not
    make the init<whatever> function public by putting
    /EXPORT:init<whatever> on the linker line, but that doesn't seem to be
    what GNU ld understands

    Any suggestions?

    Thanks,
    -Chris
    Chris Hodapp, Dec 16, 2003
    #1
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  2. Hello,
    I am not at my home office at the moment but you will probably find the
    following link helpful:

    http://groups.google.de/groups?hl=de&lr=&ie=UTF-8&oe=utf-
    8&threadm=mailman.999029862.20314.python-
    list%40python.org&rnum=7&prev=/groups%3Fhl%3Dde%26ie%3DUTF-8%26oe%3Dutf-
    8%26q%3Dpython%2Bdistutils%2Bexport%26sa%3DN%26tab%3Dwg

    The content is:
    Section 5.2 of the Extending and Embedding the Python Interpreter says:
    "The problem is that some entry points are defined by the Python runtime
    solely for extension modules to use. If the embedding application does not
    use any of these entry points, some linkers will not include those entries
    in the symbol table of the finished executable. Some additional options are
    needed to inform the linker not to remove these symbols.
    Determining the right options to use for any given platform can be quite
    difficult, but fortunately the Python configuration already has those
    values.
    To retrieve them from an installed Python interpreter, start an interactive
    interpreter and have a short session like this:
    >>> import distutils.sysconfig
    >>> distutils.sysconfig.get_config_var('LINKFORSHARED')

    '-Xlinker -export-dynamic'
    The contents of the string presented will be the options that should be
    used.
    If the string is empty, there's no need to add any additional options. The
    LINKFORSHARED definition corresponds to the variable of the same name in
    Python's top-level Makefile."
    The '-Xlinker' tells gcc to pass '-export-dynamic' to ld. gcc itself seems
    to ignore it otherwise.

    Richard Sharp

    (Chris Hodapp) wrote in
    <>:

    >I have seen messages posted about this before, and there is a clear
    >reference to it in the manual, but I have been unable to find a
    >solution.
    >
    >I'm on Slackware 9.1, kernel 2.6.0-test11, using Python 2.3.1 and
    >GCC 3.2.3 (both installed by default with Slackware) and SWIG 1.3.19,
    >compiled from source code.
    >I messed around a little on my own and couldn't get things to work
    >right,
    >so I copied the examples from the book, nearly verbatim but with some
    >minor changes to fit my configuration.
    >
    >I copied the example code exactly into example.i and example.c, and
    >did
    >the following commands:
    >swig -python example.i
    >gcc -c example.c example_wrap.c -I/usr/include/python2.3
    >ld -shared example.o example_wrap.o -o _example.so
    >... and several other times in the last command I tried some other
    >things like examplemodule.so and example.so. All of these worked
    >without
    >error, so I tried it from within Python, and got the usual error about
    >"ImportError: dynamic module does not define init function" when I
    >tried
    >'import example'. It made no difference if I added the path with all
    >the
    >files to sys.path; the same error occurred.
    >
    >I tried this several times over, and I could never get it to work
    >right. The last helpful suggestion I saw on here was that I did not
    >make the init<whatever> function public by putting
    >/EXPORT:init<whatever> on the linker line, but that doesn't seem to be
    >what GNU ld understands
    >
    >Any suggestions?
    >
    >Thanks,
    >-Chris
    >
    Richard Sharp, Dec 16, 2003
    #2
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  3. Chris Hodapp

    Chris Hodapp Guest

    (Richard Sharp) wrote in message news:<brmf66$4qq93$-berlin.de>...
    > Hello,
    > I am not at my home office at the moment but you will probably find the
    > following link helpful:
    >
    > http://groups.google.de/groups?hl=de&lr=&ie=UTF-8&oe=utf-
    > 8&threadm=mailman.999029862.20314.python-
    > list%40python.org&rnum=7&prev=/groups%3Fhl%3Dde%26ie%3DUTF-8%26oe%3Dutf-
    > 8%26q%3Dpython%2Bdistutils%2Bexport%26sa%3DN%26tab%3Dwg
    >

    <snip>
    >
    > Richard Sharp
    >


    Thank you. That information, along with GCC's manual pages, helped me
    to get everything working. What eventually worked was 'gcc example.c
    example_wrap.c -I/usr/include/python-2.3 -Xlinker -export-dynamic
    -shared -o _example.c'.

    -Chris
    Chris Hodapp, Dec 17, 2003
    #3
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