fix script timeout bug (#170)

* fix an edge case where script timeout is too short and set even before VM starts execution

* vm.StackObjects() -> v.IsStackEmpty()

runtime/vm.go

@@ -77,7 +77,6 @@ func (v *VM) Run() (err error) {
 	v.framesIndex = 1
 	v.ip = -1
 	v.allocs = v.maxAllocs + 1
-	atomic.StoreInt64(&v.aborting, 0)
 
 	v.run()
 
@@ -95,11 +94,6 @@ func (v *VM) Run() (err error) {
 		return err
 	}
 
-	// check if stack still has some objects left
-	if v.sp > 0 && atomic.LoadInt64(&v.aborting) == 0 {
-		panic(fmt.Errorf("non empty stack after execution: %d", v.sp))
-	}
-
 	return nil
 }
 
@@ -121,7 +115,7 @@ func (v *VM) run() {
 		}
 	}()
 
-	for atomic.LoadInt64(&v.aborting) == 0 {
+	for atomic.CompareAndSwapInt64(&v.aborting, 0, 0) {
 		v.ip++
 
 		switch v.curInsts[v.ip] {
@@ -1008,9 +1002,9 @@ func (v *VM) run() {
 	}
 }
 
-// Globals returns the global variables.
+// IsStackEmpty tests if the stack is empty or not.
-func (v *VM) Globals() []objects.Object {
+func (v *VM) IsStackEmpty() bool {
-	return v.globals
+	return v.sp == 0
 }
 
 func indexAssign(dst, src objects.Object, selectors []objects.Object) error {

runtime/vm_test.go

@@ -1,6 +1,7 @@
 package runtime_test
 
 import (
+	"errors"
 	"fmt"
 	"reflect"
 	_runtime "runtime"
@@ -250,8 +251,8 @@ func traceCompileRun(file *ast.File, symbols map[string]objects.Object, modules
 		}
 		trace = append(trace, fmt.Sprintf("\n[Globals]\n\n%s", strings.Join(formatGlobals(globals), "\n")))
 	}
-	if err != nil {
+	if err == nil && !v.IsStackEmpty() {
-		return
+		err = errors.New("non empty stack after execution")
 	}
 
 	return