$Id: README.modules,v 1.2 2003/04/14 17:54:23 jeff Exp $

Oracle does not support (nor does it work anyway) the dynamic loading of
shared objects from an external procedure.  Therefore, the use of the dl*
functions on Solaris or the dld_* functions on Linux is not permitted,
rendering Perl's DynaLoader useless.  What does this mean?  It means that
we can't use DynaLoader to dynamically load Perl modules containing shared
objects.  Perl-only modules remain unaffected, as there are no shared objects
to load.

To get around this problem, extproc_perl loads shared objects from the modules
at run-time by linking with them after compilation.  This lets the operating
system properly load in the shared objects, avoiding DynaLoader altogether.
It is analogous to statically linking each module into the Perl interpreter.
The only thing that needs to be done is to initialize the modules by
providing hooks into each module's bootstrap function.  We do this by
creating a special file, perlxsi.c, that contains the XS initialization code.
This code is created for us by the ExtUtils::Embed module, and is statically
linked into the extproc_perl shared library.

Unfortunately, this method requires us to know ahead of time which modules we
want to use, as their shared objects need to be linked to the extproc_perl
library, and their bootstrap code must be made available to Perl.  If you
install a new module that uses shared objects, extproc_perl will have to be
recompiled to use that module.

How do we find the shared objects for each module?  The gen_module_libs script 
asks Perl itself where to search for them.  In particular, it looks in
installarchlib, installsitelib, and installprivlib, all of which are available
through use of the Config module.  gen_module_libs then searches those
directory trees for paths that match each module's name and looks for files
ending with the platform's shared object extension ($Config{dlext}).  These
files are linked with the final extproc_perl library so they are loaded at
run-time.

This method of loading modules has been tested on Solaris 8 and Linux 2.4.
