I tried to write a native hdfs client using protobuf based protocol, when I generate c++ code using hdfs.proto, the generated file can not compile, because NULL is an already defined macro.
I am thinking two solutions:
1. refactor all DataChecksum.Type.NULL references to NONE, which should be fine for all languages, but this may breaking compatibility.
2. only change protobuf definition ChecksumTypeProto.NULL to NONE, and use enum integer value(DataChecksum.Type.id) to convert between ChecksumTypeProto and DataChecksum.Type, and make sure enum integer values are match(currently already match).
I can make a patch for solution 2.