Initial callback handling.

It works, but it'll leak memory since all the information needed to handle a
callback is recreated (and allocated on the heap) on each call without ever
being freed.

src/6model/reprs/NativeCall.c

@@ -77,6 +77,8 @@ static void gc_cleanup(PARROT_INTERP, STable *st, void *data) {
         dlFreeLibrary(body->lib_handle);
     if (body->arg_types)
         mem_sys_free(body->arg_types);
+    if (body->arg_info)
+        mem_sys_free(body->arg_info);
 }
 
 /* This Parrot-specific addition to the API is used to free an object. */
@@ -86,6 +88,18 @@ static void gc_free(PARROT_INTERP, PMC *obj) {
     PMC_data(obj) = NULL;
 }
 
+static void gc_mark(PARROT_INTERP, STable *st, void *data) {
+    NativeCallBody *body = (NativeCallBody *)data;
+
+    if (body->arg_info) {
+        INTVAL i;
+        for (i = 0; i < body->num_args; i++) {
+            if (body->arg_info[i])
+                Parrot_gc_mark_PMC_alive(interp, body->arg_info[i]);
+        }
+    }
+}
+
 /* Gets the storage specification for this representation. */
 static storage_spec get_storage_spec(PARROT_INTERP, STable *st) {
     storage_spec spec;

src/6model/reprs/NativeCall.h

@@ -1,8 +1,9 @@
 #ifndef NATIVECALL_H_GUARD
 #define NATIVECALL_H_GUARD
 
-#include "dyncall/dyncall.h"
-#include "dynload/dynload.h"
+#include "dyncall.h"
+#include "dynload.h"
+#include "dyncall_callback.h"
 
 /* Body of a NativeCall. */
 typedef struct {
@@ -13,6 +14,7 @@ typedef struct {
     INTVAL num_args;
     INTVAL *arg_types;
     INTVAL ret_type;
+    PMC **arg_info;
 } NativeCallBody;
 
 /* This is how an instance with the NativeCall representation looks. */