[q-lang-users] Re: modules in c++

[Brian W. <drc...@gm...>]

Hello again,

(I should probably always just wait to email the list until I've done
the "next" bit of research...)

Here's what I've figured out:

1) The quoted errors can be "fixed" with the following patch to libq.h:
----------------- patch.libq.h ----------------------
*** libq.1.6.h=09Wed Oct 20 01:09:42 2004
--- libq.h=09Fri Aug 26 15:38:04 2005
***************
*** 127,135 ****
--- 127,141 ----
 =20
  /* Predefined function and type symbols. */
 =20
+ #ifdef __cplusplus
+ __DLLIMPORT  int truesym, falsesym, nilsym, voidsym;
+ __DLLIMPORT  int inttype, floattype, booltype, strtype, filetype,
+   listtype, tupletype;
+ #else
  __DLLIMPORT const int truesym, falsesym, nilsym, voidsym;
  __DLLIMPORT const int inttype, floattype, booltype, strtype, filetype,
    listtype, tupletype;
+ #endif
 =20
  /* Expression construction. */

----------------------------------------------------
The upshot is that _DLLIMPORT const... is not a happy thing in C++.

BUT, not knowing what the heck I'm doing, I don't know what else I've
broken. Someone should correct this change before anyone uses it.

2) Also, the cpp source file needs to be changed to protect the
exports from name-mangling by enclosing everything in extern "C" {}.
The bar.cpp example becomes:
------------------- bar.cpp --------------------
#include <libq.h>

extern "C" {

  MODULE(bar)

    typedef struct { long i, j; } Bar;

  FUNCTION(bar,bar,argc,argv)
  {
    long i, j;
    if (argc !=3D 2 || !isint(argv[0], &i) || !isint(argv[1], &j))
      return __FAIL;
    else {
      Bar *v =3D (Bar *)malloc(sizeof(Bar));
      expr x;
      if (!v) return __ERROR;
      v->i =3D i; v->j =3D j;
      return mkobj(type(Bar), v);
    }
  }

  FUNCTION(bar,dump,argc,argv)
  {
    long i, j;
    Bar *v;
    if (argc !=3D 1 || !isobj(argv[0], type(Bar), (void **)&v))
      return __FAIL;
    else {
      printf( "i =3D %d, j =3D %d\n", v->i, v->j);
      return mkint( 0);
    }
  }

}
-------------------------------------------------

Just for completeness, here's the .q file that goes with this:
-------------------- bar.q --------------------
// Type Bar

public extern type Bar;
public extern bar I J; // I, J: integer
public extern dump A; // A: Bar

test =3D dump (bar 5 3) ||
=09dump (bar 1000 25);
------------------------------------------------

Lemme know what you think.

Brian