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(Guile Support Internals): New h2, numbered 10.

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Push "Miscellaneous" to 11.


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Thien-Thi Nguyen 2000-04-03 14:38:30 +00:00
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@ -401,10 +401,97 @@ you to change the internal representation of Foo without breaking all
of the other modules or having to recompile the entire universe after
making your changes.
<h3>10. Miscellaneous </h3>
<h2>10. Guile Support Internals</h2>
Please direct questions about this section to
<a href="mailto:ttn@glug.org">ttn@glug.org</a>.
Last update: 2000-04-03 05:27:34-0700.
<h3>Meaning of "Module"</h3>
<p>
There are three different concepts of "module" involved, defined separately
for SWIG, Guile, and Libtool. To avoid horrible confusion, we explicitly
prefix the context, e.g., "guile-module".
<h3>Linkage</h3>
<p>
Guile support is complicated by a lack of user community cohesiveness, which
manifests in multiple shared-library usage conventions. A set of policies
implementing a usage convention is called a <b>linkage</b>. The default
linkage is the simplest; nothing special is done. In this case `SWIG_init()'
is provided and users must do something like this:
<blockquote>
<pre>
(define my-so (dynamic-link "./example.so"))
(dynamic-call "SWIG_init" my-so)
</pre>
</blockquote>
At this time, the name `SWIG_init' is hardcoded; this approach does not work
with multiple swig-modules.
<p>
A second linkage creates "libtool dl module" wrappers, and currently is
broken. Whoever fixes this needs to track Guile's libtool dl module
convention, since that is not finalized.
<p>
The only other linkage supported at this time creates shared object libraries
suitable for use by hobbit's `(hobbit4d link)' guile module. This is called
the "hobbit" linkage, and requires also using the "-package" command line
option to set the part of the module name before the last symbol. For
example, both command lines: [checkme:ttn]
<blockquote>
<pre>
swig -guile -package my/lib foo.i
swig -guile -package my/lib -module foo foo.i
</pre>
</blockquote>
would create module `(my lib foo)' (assuming in the first case foo.i declares
the module to be "foo"). The installed files are my/lib/libfoo.so.X.Y.Z and
friends. This scheme is still very experimental; the (hobbit4d link)
conventions are not well understood.
<p>
There are no other linkage types planned, but that could change... To add a
new type, add the name to the enum in guile.h and add the case to
`GUILE::emit_linkage()'.
<h3>Underscore Folding</h3>
<p>
Underscores are converted to dashes in identifiers. Guile support may grow an
option to inhibit this folding in the future, but no one has complained so
far.
<h3>Typemaps</h3>
<p>
It used to be that the mappings for "native" types were included in
guile.cxx. This information is now in Lib/guile/typemaps.i, which presents a
new challenge: how to have SWIG include typemaps.i before processing the
user's foo.i. At this time, we must say:
<blockquote>
<pre>
%include guile/typemaps.i
</pre>
</blockquote>
in foo.i. This may change in the future.
<h2>11. Miscellaneous </h2>
<ul>
<li> Do not use the ternary ?: operator. It is unnecessarily error prone,
hard for people to read, and hard to maintain code that uses it.
</ul>
</body>
</html>