Merge pull request #1874 from nspcc-dev/fix-states-diff

vm: minor C# compatibility fixes

pkg/core/interop/runtime/engine.go

@@ -52,11 +52,11 @@ func GetTrigger(ic *interop.Context) error {
 // in neo-go the only meaningful thing to do here is to log.
 func Notify(ic *interop.Context) error {
 	name := ic.VM.Estack().Pop().String()
+	elem := ic.VM.Estack().Pop()
+	args := elem.Array()
 	if len(name) > MaxEventNameLen {
 		return fmt.Errorf("event name must be less than %d", MaxEventNameLen)
 	}
-	elem := ic.VM.Estack().Pop()
-	args := elem.Array()
 	// But it has to be serializable, otherwise we either have some broken
 	// (recursive) structure inside or an interop item that can't be used
 	// outside of the interop subsystem anyway.

pkg/core/interop/runtime/engine_test.go

@@ -142,7 +142,7 @@ func TestNotify(t *testing.T) {
 		return ic
 	}
 	t.Run("big name", func(t *testing.T) {
-		ic := newIC(string(make([]byte, MaxEventNameLen+1)), []byte{42})
+		ic := newIC(string(make([]byte, MaxEventNameLen+1)), stackitem.NewArray([]stackitem.Item{stackitem.Null{}}))
 		require.Error(t, Notify(ic))
 	})
 	t.Run("recursive struct", func(t *testing.T) {

pkg/vm/vm.go

@@ -1304,7 +1304,7 @@ func (v *VM) execute(ctx *Context, op opcode.Opcode, parameter []byte) (err erro
 		interopID := GetInteropID(parameter)
 		err := v.SyscallHandler(v, interopID)
 		if err != nil {
-			panic(fmt.Sprintf("failed to invoke syscall: %s", err))
+			panic(fmt.Sprintf("failed to invoke syscall %d: %s", interopID, err))
 		}
 
 	case opcode.RET:
@@ -1602,8 +1602,32 @@ func (v *VM) handleException() {
 		}
 		pop++
 		ictxv = ictxv.Next()
+		if ictxv == nil {
+			break
+		}
 		ictx = ictxv.Value().(*Context)
 	}
+	throwUnhandledException(v.uncaughtException)
+}
+
+// throwUnhandledException gets exception message from the provided stackitem and panics.
+func throwUnhandledException(item stackitem.Item) {
+	msg := "unhandled exception"
+	switch item.Type() {
+	case stackitem.ArrayT:
+		if arr := item.Value().([]stackitem.Item); len(arr) > 0 {
+			data, err := arr[0].TryBytes()
+			if err == nil {
+				msg = fmt.Sprintf("%s: %q", msg, string(data))
+			}
+		}
+	default:
+		data, err := item.TryBytes()
+		if err == nil {
+			msg = fmt.Sprintf("%s: %q", msg, string(data))
+		}
+	}
+	panic(msg)
 }
 
 // CheckMultisigPar checks if sigs contains sufficient valid signatures.