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(python2.1-ext.info)Linking Requirements

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Linking Requirements
====================

While the `configure' script shipped with the Python sources will
correctly build Python to export the symbols needed by dynamically
linked extensions, this is not automatically inherited by applications
which embed the Python library statically, at least on UNIX.  This is
an issue when the application is linked to the static runtime library
(`libpython.a') and needs to load dynamic extensions (implemented as
`.so' files).

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'.