Implement RB_GC_GUARD.

Author: aardvark179

lib/cext/include/ruby/ruby.h

@@ -498,10 +498,11 @@ MUST_INLINE int RB_FLOAT_TYPE_P(VALUE obj);
 
 bool RB_TYPE_P(VALUE value, int type);
 
-#define HAVE_RB_GC_GUARDED_PTR_VAL 1
-#define rb_gc_guarded_ptr_val(ptr, val) (ptr)
-#define RB_GC_GUARD(v) (v)
-#define RB_GC_GUARD_PTR(ptr) (ptr)
+#define RB_GC_GUARD(v) \
+    (*__extension__ ({ \
+        VALUE *rb_gc_guarded_ptr = rb_tr_gc_guard(v);   \
+        rb_gc_guarded_ptr;                              \
+    }))
 
 #ifdef __GNUC__
 #define RB_UNUSED_VAR(x) x __attribute__ ((unused))

lib/cext/include/truffleruby/truffleruby-pre.h

@@ -48,6 +48,14 @@ MUST_INLINE VALUE rb_tr_unwrap(VALUE object) {
   return polyglot_invoke(RUBY_CEXT, "rb_tr_unwrap", object);
 }
 
+// Needed for GC guarding
+
+MUST_INLINE VALUE *rb_tr_gc_guard(VALUE v) {
+  VALUE *ptr = &v;
+  polyglot_invoke(RUBY_CEXT, "rb_tr_gc_guard", v);
+  return ptr;
+}
+
 #include <ruby/thread_native.h>
 
 // Helpers

src/main/java/org/truffleruby/cext/CExtNodes.java

@@ -1384,6 +1384,32 @@ protected UnwrapNode createUnwrapNode() {
         }
     }
 
+    @CoreMethod(names = "rb_tr_gc_guard", onSingleton = true, required = 1)
+    public abstract static class GCGuardNode extends CoreMethodArrayArgumentsNode {
+
+        @Specialization
+        public DynamicObject addToMarkList(VirtualFrame frmae, Object guardedObject,
+                @Cached("create()") BranchProfile exceptionProfile,
+                @Cached("create()") UnwrapNode.ToWrapperNode toWrapperNode) {
+            ValueWrapper wrappedValue = toWrapperNode.execute(guardedObject);
+            if (wrappedValue == null) {
+                exceptionProfile.enter();
+                throw new RaiseException(getContext(), coreExceptions().runtimeError(exceptionMessage(guardedObject), this));
+            }
+            getContext().getMarkingService().keepObject(guardedObject);
+            return nil();
+        }
+
+        @TruffleBoundary
+        private String exceptionMessage(Object value) {
+            return String.format("native handle not found (%s) to guard it", value);
+        }
+
+        protected UnwrapNode createUnwrapNode() {
+            return UnwrapNodeGen.create();
+        }
+    }
+
     @CoreMethod(names = "set_mark_list_on_object", onSingleton = true, required = 1)
     public abstract static class SetMarkList extends CoreMethodArrayArgumentsNode {