test.c

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#ifdef _WIN32
#define DLLEXPORT __declspec(dllexport)
#else
#define DLLEXPORT extern
#endif

struct Point {
  int x;
  int y;
};

DLLEXPORT void * ReturnSomePointer()
{
    return strdup("Got passed back the pointer I returned");
}

DLLEXPORT int CompareSomePointer(void *ptr)
{
    int x = strcmp("Got passed back the pointer I returned", ptr) == 0;
    free(ptr);
    return x;
}

DLLEXPORT void * ReturnNullPointer()
{
    return NULL;
}

DLLEXPORT void * TakeTwoPointersToInt(int *ptr1, int *ptr2)
{
    return NULL;
}

DLLEXPORT void * TakeCArrayToInt8(int array[]) {
    return NULL;
}

DLLEXPORT void  NewPoint(struct Point *p)
{
    p = malloc(sizeof(struct Point));
    p->x = 42;
    p->y = 42;
}

DLLEXPORT void  NewPointPtr(struct Point **p)
{
    printf("NewPointPtr\n");
    *p = malloc(sizeof(struct Point));
    (*p)->x = 42;
    (*p)->y = 42;
}

test.p6

class Point is repr('CStruct') {
  has   int32   $.x;
  has   int32   $.y;
}


sub NewPointPtr(Pointer[Pointer[Point]] is rw) is native("./04-pointers") { * };

my Pointer[Pointer[Point]] $ptr2 .= new;
say "Pass ptr to C";
NewPointPtr($ptr2);
say "Hello";
my Point $p = $ptr2.deref.deref;

ok $p.x == 42 and $p.y == 42;