[protobuf] Protocol Buffers Version 21.2 is Released!

This version includes the following non-breaking changes: C++ * ArenaString improvements (fix alignment issue) PHP * API changes for OneOf (#10102) You can view the release on [GitHub]( https://github.com/protocolbuffers/protobuf/releases/tag/v21.2). If you experience any issues with the

[protobuf] Re: Message Definition

#1 for achieving "constants" the use of enums and default tag would give you what you want, but this is only permitted in proto2 example: //Enums default to their zero value. By not using 0, you ensure a message is always explicitly set. enum MessageType { MSG_TYPE_INVALID = 0; MSG_TYPE_1 = 1;