Re: More questions about writing extensions.

[Matthew Flatt <mflatt@cs.utah.edu>]

Quoting Robert John Andersen:
>   Lets say I have 2 libraries that i want to interface to, lib1 and lib2 and
> lib2 uses lib1.  I also have an additional .module that I created for
> miscellaneous stuff that my libraries (mylib1, mylib2) will use.  When
> using my module should I create an so and if so where can I put it so that
> mylib1.so and mylib2.so can pick it up?  Does it have to be in the users
> LD_LIBRARY_PATH or users /etc/ld.so.conf or can I put it in the PLT
> directories somewhere?

You can probably set LD_LIBRARY_PATH before calling `load-extension'.
It worked for me under Linux, at least. Here's an example where b.so
needs helper.so:

  % cd /home/mflatt/tmp
  % mzc --ld b.so b.o helper.so
  % cd ..
  % mzscheme
  Welcome to MzScheme ...
  > (load-extension "tmp/b.so")
  load-extension: couldn't open "/usr/home/mflatt/tmp/b.so" (helper.so:
  cannot open shared object file: No such file or directory)
  > (putenv "LD_LIBRARY_PATH" "/home/mflatt/tmp/")
  #t
  > (load-extension "tmp/b.so")
  -2

where -2 was the expected result.

>   I would like to be able to write 2 shareable objects mylib1.so and
> mylib2.so and be able to load just mylib1.so or load mylib2.so and
> mylib1.so.  I was wondering if I could accomplish this with using units and
> having the files mylib1.ss and mylib2.ss?

Yes. If mylib1.so and mylib2.so produce units, then mylib1.ss could
return the mylib1.so unit, and mylib2.ss could return a compound unit
linking the mylib1.so and mylib2.so units.

Matthew