How to pass two dimensional arrays to C

["Jerry" <lanceboyle@qwest.net>]

In my project to write a binding for a popular plotter written in C,
I've hit a brick wall and the problem might be associated with passing
two-dimensionaal arrays to C. I'm using GNAT on OS X and Xcode. I can
pass one-dimensional arrays OK. Here are the pertinent parts from an
example where the problem happens:


      The C


typedef double PLFLT;
typedef int PLINT;

void c_plmesh(PLFLT *x, PLFLT *y, PLFLT **z, PLINT nx, PLINT ny, PLINT
opt);



      The Ada


type Long_Float_Array_1D is array (Integer range <>) of Long_Float;
type Long_Float_Array_2D is array (Integer range <>, integer range <>)
of Long_Float;

subtype PLINT  is Integer;

subtype PL_Float_Array    is Long_Float_Array_1D;
subtype PL_Float_Array_2D is Long_Float_Array_2D;

procedure plmesh(
    x   : PL_Float_Array;
    y   : PL_Float_Array;
    z   : PL_Float_Array_2D;
    nx  : PLINT;
    ny  : PLINT;
    opt : PLINT);
pragma Import(C, plmesh, "c_plmesh");



      And the Ugly


AdaPLplotProject has exited due to signal 11 (SIGSEGV).

This appears during the call to plmesh. Any ideas? 

Thanks,
Jerry