[Vala] Problem while creating a vapi file for a typedef'd pointer.

[Geoffrey Blackman <geoff gblackman co uk>]

Hi,
I'm attempting to create a vapi file for Verilog VPI and have run into a
problem with a opaque pointer type.
Different implementations of VPI define the type vpiHandle differently. Two
examples are

typedef void *vpiHandle;
typedef struct __vpiHandle *vpiHandle;

I therefor need to define a type in my vapi file which will map to vpiHandle
and behave like a pointer.
My initial atempts look something like the following.

namespace Vpi {
    [CCode (cname="PLI_INT32", cprefix="vpi")]
    public enum Type {
        SysTfCall,
        Argument
    }

    [SimpleType]
    [CCode (cname = "vpiHandle", free_function="vpi_free_object")]
    public struct Handle {
        [CCode (cname="vpi_iterate", instance_pos=2 )]
        public Handle? iterate(Type type);
    }

    [CCode (cname="vpi_handle")]
    public static Handle GetHandle(Type type, Handle? r);
}


using Vpi;
public class Test {
    public static int calltf(string? user_data) {
        Handle p = GetHandle(Vpi.Type.SysTfCall, null);
        Handle? argv = p.iterate(Vpi.Type.Argument);
        if (argv != null) {
            // do something...
        }
        return 0;
    }
}

Which generates the following code
gint test_calltf (const char* user_data) {
    vpiHandle p;
    vpiHandle* argv;
    gint _tmp0;
    p = vpi_handle (vpiSysTfCall, NULL);
    argv = vpi_iterate (vpiArgument, p);
    if (&argv != NULL) {
    }
    /* do something...*/
    return (_tmp0 = 0, (argv == NULL ? NULL : (argv = (g_free (argv),
NULL))), _tmp0);
}

Note that the '?' indicating that the iterate method can return null has
caused argv to have type 'vpiHandle*' rather than the vpiHandle returned by
vpi_iterate.
If I remove the nullable marker I would get the correct type for argv,
however I cannot now test it for null.

Equality operation: `null' and `Vpi.Handle' are incompatible

For reference, the code I am trying to have generated would look something
like

    vpiHandle p;
    vpiHandle argv;
    p = vpi_handle (vpiSysTfCall, NULL);
    argv = vpi_iterate (vpiArgument, p);
    if (argv != NULL) {
        // do something...
    }

Any help in correctly defining vpiHandle would be apreciated.

Thanks

--
Geoff Blackman