Possible dereference

[Bbulatov]

Hello!
During the static analysis was found possible mistake:

1. After having been compared to a nil value at stream.go:1029, pointer 'cs.attempt' is passed in call to function 'grpc.clientStream.Trailer' at stream.go:1053, where it is dereferenced at stream.go:858.

default:
			logEntry := &binarylog.ServerTrailer{
				OnClientSide: true,
				Trailer:      cs.Trailer(),
				Err:          err,
			}

version of gRPC: master
version of Go: go version go1.22.4 linux/amd64
operating system: Linux debian 10

[aranjans]

Thanks for raising this issue and bringing it to our attention. The static analysis you're using might be flagging a false positive here.

Let's break down why:

• cs.attempt initialization: The cs.attempt field is initially nil, but it's populated within the newClientStreamWithParams function before being used in any critical operations.

• Guaranteed non-nil in Trailer(): The Trailer() method is called only after the stream is considered finished, either successfully or due to an error. By this point, cs.attempt is guaranteed to be non-nil. This is ensured because:

  • A successful stream creation would have assigned a value to cs.attempt.
  • An error during stream creation would lead to the finish method being called, which handles the case of cs.attempt potentially being nil.
  • finish() method's safeguard: The finish() method itself includes a check (if cs.attempt != nil) to prevent nil pointer dereferences in scenarios where the stream might not have been fully established.

If you can provide a minimal, reproducible example that demonstrates the issue, that would be even more helpful in diagnosing the problem.