Release value memory on context close (#78)

* Release value memory on context close

* retry test with a larger number of contexts

* no need to re-cast

* Update changelog and release v0.5.1

CHANGELOG.md

@@ -6,6 +6,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [v0.5.1] - 2021-02-19
+
+### Fixed
+- Memory being held by Values after the associated Context is closed
+
 ## [v0.5.0] - 2021-02-08
 
 ### Added

context.go

@@ -116,11 +116,11 @@ func (c *Context) RunScript(source string, origin string) (*Value, error) {
 func (c *Context) Global() *Object {
 	valPtr := C.ContextGlobal(c.ptr)
 	v := &Value{valPtr, c}
-	runtime.SetFinalizer(v, (*Value).finalizer)
 	return &Object{v}
 }
 
 // Close will dispose the context and free the memory.
+// Access to any values assosiated with the context after calling Close may panic.
 func (c *Context) Close() {
 	c.finalizer()
 }
@@ -165,13 +165,17 @@ func getContext(ref int) *Context {
 	return r.ctx
 }
 
+//export goContext
+func goContext(ref int) C.ContextPtr {
+	ctx := getContext(ref)
+	return ctx.ptr
+}
+
 func getValue(ctx *Context, rtn C.RtnValue) *Value {
 	if rtn.value == nil {
 		return nil
 	}
-	v := &Value{rtn.value, ctx}
-	runtime.SetFinalizer(v, (*Value).finalizer)
-	return v
+	return &Value{rtn.value, ctx}
 }
 
 func getError(rtn C.RtnValue) error {

context_test.go

@@ -92,6 +92,23 @@ func TestContextRegistry(t *testing.T) {
 	}
 }
 
+func TestMemoryLeak(t *testing.T) {
+	t.Parallel()
+
+	iso, _ := v8go.NewIsolate()
+
+	for i := 0; i < 6000; i++ {
+		ctx, _ := v8go.NewContext(iso)
+		obj := ctx.Global()
+		_ = obj.String()
+		_, _ = ctx.RunScript("2", "")
+		ctx.Close()
+	}
+	if n := iso.GetHeapStatistics().NumberOfNativeContexts; n >= 6000 {
+		t.Errorf("Context not being GC'd, got %d native contexts", n)
+	}
+}
+
 func BenchmarkContext(b *testing.B) {
 	b.ReportAllocs()
 	vm, _ := v8go.NewIsolate()

function_template.go

@@ -70,7 +70,6 @@ func goFunctionCallback(ctxref int, cbref int, args *C.ValuePtr, argsCount int)
 	argv := (*[1 << 30]C.ValuePtr)(unsafe.Pointer(args))[:argsCount:argsCount]
 	for i, v := range argv {
 		val := &Value{ptr: v}
-		runtime.SetFinalizer(val, (*Value).finalizer)
 		info.args[i] = val
 	}