gcc-3.0 dynamic loading broken, preliminary patch for feedback

[John W. Eaton]

On 28-Jun-2001, Mumit Khan <address@hidden> wrote:

| Those of who're trying out Octave CVS with gcc-3.0, you'll notice that
| dynamic loading is broken, something that I had completely missed. Thanks
| to Christoph Spiel for pointing out the obvious.
| 
| I have a preliminary patch that does the right thing depending on GNU C++
| ABI (v2 aka old, or v3 aka new, and supposedly forever stable), but I need
| to write up a autoconf macro for this, and take care of a few other gritty
| details such as checking for underscore prefix etc.
| 
| I'm including a temporary patch, but please don't depend on this. This is
| not meant to go into CVS as is. I'm looking for feedback at this point on
| how to do this correctly. I have thought about including the GNU C++
| demangling code, but that's a bit more work than I'd like to do at this
| point.

I see two other possibilities.  One is to just try to find the symbol
with each type of mangling in turn.  Then you don't need to know the
type of mangling in advance.  Perhaps the mangling function could even
be defined in a .m file, so that people could more easily customize
it.  Although this would slow things down a bit, I don't think it
matters much, because the overhead of evaluating the .m file would
only take place once, when the function is first loaded from the .oct
file.

Another is to eliminate the need for mangling, by declaring the
installer function extern "C".  I think It would be easy to do this,
by modifying the DEFINE_FUN_INSTALLER_FUN macro in defun-int.h to be:

  #define DEFINE_FUN_INSTALLER_FUN(name, doc) \
    extern "C" bool \
    FS ## name (const octave_shlib& shl) \
    { \
      check_version (OCTAVE_VERSION, #name); \
      install_dld_function (F ## name, #name, shl, doc); \
      return error_state ? false : true; \
    }

but I'm not sure wheter this will work.  Can you define extern "C"
functions that have class names and non-C types as arguments?  If this
is possible and we choose this solution, perhaps the prefix FS should
be made more descriptive.

jwe