Merge pull request #4887 from davecheney/fixedbug/14904

apiserver/client: work around compiler bug with named return values

Upstream golang/go#14904

Returning a complex variable by value with a mix of named and implicit
returns was throwing off the compiler. This caused the memory occupied
by the return value to be considered dead before the end of the
function, leading to the gc freeing that memory prematurely.

The bug is not believed to not affect any shipping Go 1.6 compiler, but
it seems prudent to work around the compiler issue in our code.

(Review request: http://reviews.vapour.ws/r/4336/)

apiserver/client/status.go

@@ -598,11 +598,13 @@ func (context *statusContext) processServices() map[string]params.ServiceStatus
 	return servicesMap
 }
 
-func (context *statusContext) processService(service *state.Service) (processedStatus params.ServiceStatus) {
+func (context *statusContext) processService(service *state.Service) params.ServiceStatus {
 	serviceCharmURL, _ := service.CharmURL()
-	processedStatus.Charm = serviceCharmURL.String()
-	processedStatus.Exposed = service.IsExposed()
-	processedStatus.Life = processLife(service)
+	var processedStatus = params.ServiceStatus{
+		Charm:   serviceCharmURL.String(),
+		Exposed: service.IsExposed(),
+		Life:    processLife(service),
+	}
 
 	if latestCharm, ok := context.latestCharms[*serviceCharmURL.WithRevision(-1)]; ok && latestCharm != nil {
 		if latestCharm.Revision() > serviceCharmURL.Revision {
@@ -614,20 +616,20 @@ func (context *statusContext) processService(service *state.Service) (processedS
 	processedStatus.Relations, processedStatus.SubordinateTo, err = context.processServiceRelations(service)
 	if err != nil {
 		processedStatus.Err = err
-		return
+		return processedStatus
 	}
 	networks, err := service.Networks()
 	if err != nil {
 		processedStatus.Err = err
-		return
+		return processedStatus
 	}
 	var cons constraints.Value
 	if service.IsPrincipal() {
 		// Only principals can have constraints.
 		cons, err = service.Constraints()
 		if err != nil {
 			processedStatus.Err = err
-			return
+			return processedStatus
 		}
 	}
 	// TODO(dimitern): Drop support for this in a follow-up.
@@ -646,7 +648,7 @@ func (context *statusContext) processService(service *state.Service) (processedS
 		serviceStatus, err := service.Status()
 		if err != nil {
 			processedStatus.Err = err
-			return
+			return processedStatus
 		}
 		processedStatus.Status.Status = serviceStatus.Status
 		processedStatus.Status.Info = serviceStatus.Message