Getting rid of warnings in Qhull related code, and confhulln() issues

[Daniel J Sebald]

John,

The other day we discussed Flex and the fact there is a C++ interface in 
t works.  Apparently the same is true of Qhull.  E.g.,

http://gitorious.org/qhull/qhull/blobs/master/src/libqhullcpp/Qhull.h

Not sure it is worth the effort in this case (given how small the 
code/macro use is in Octave).  In the long run, perhaps.  But I think 
there might be a better way of suppressing the warnings.

Before getting any further, I'd like to point out some things about 
convhulln.cc.

I've attached a small change that replaces a "return" with a "break". 
If the routine were to return inside that loop (which I don't think it 
currently does), there would be a memory leak.  That is, the memory 
created by the qhull routines wouldn't be freed after the end of the loop.

The conditional test breaks out of the loop if there is a non-simplicial 
facet and the user specified option QJ.  It seems one can put anything 
in for options to the convhulln() routine (even nonsensical stuff) and 
it doesn't matter much.  The options don't seem to be used in any 
meaningful way, other than that QJ break out.

So, back to what initiated this--the warnings.  I was thinking a way to 
get rid of these warnings:

../../octave/libinterp/dldfcn/__voronoi__.cc: In function 
'octave_value_list F__voronoi__(const octave_value_list&, int)':
../../octave/libinterp/dldfcn/__voronoi__.cc:197:11: warning: use of 
old-style cast
../../octave/libinterp/dldfcn/__voronoi__.cc:277:11: warning: use of 
old-style cast
../../octave/libinterp/dldfcn/convhulln.cc: In function 
'octave_value_list Fconvhulln(const octave_value_list&, int)':
../../octave/libinterp/dldfcn/convhulln.cc:200:15: warning: use of 
old-style cast
../../octave/libinterp/dldfcn/convhulln.cc:211:19: warning: use of 
old-style cast
../../octave/libinterp/dldfcn/convhulln.cc:218:19: warning: use of 
old-style cast
../../octave/libinterp/dldfcn/convhulln.cc:218:19: warning: use of 
old-style cast
../../octave/libinterp/dldfcn/convhulln.cc:218:19: warning: use of 
old-style cast

is to take all the code in __voronoi__.cc and convhulln.cc that is qhull 
related and put that in a c-file called "qhcore.c" with an appropriate 
header.  Then in __voronoi__.cc and convhulln.cc would be something like:

#include "qhcore.h"
...
memptr = <create_some_memory>  // A location to store Qhull's results
qh_convhulln (dim, num_points, points.fortran_vec (),
              ismalloc, cmd_str, outfile, errfile, memptr);
Matrix idx (nf, dim + 1);
octave_idx_type i = 0;
for (; i<ilen; i++)
  {
    octave_idx_type j = 0;
    for (; j<jlen; j++)
      idx(i, j) = memptr(j + N*i);
  }
  free(memptr);

The idea is to keep all the Qhull function/macro code in a C-file and 
use a little hook to the Octave function equivalents.

Do either of these (macros in C-file, or more robust 'options') sound 
like something worth doing?

Dan

octave-convhulln-2012aug30.patch
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