Stack overflow (recursive call) in 3.7.0-rc1 (Java)

[maja42]

What version of protobuf and what language are you using?
Version: 3.7.0-rc1
Language: Java

What operating system (Linux, Windows, ...) and version?
Ubuntu 16.4

What did you do?
We have protobuf-files that are generated with an older version of the protobuf java compiler, namely protoc-3.5.1-linux-x86_64.
We updated the de Java-Dependency com.google.protobuf from 3.6.1 to 3.7.0-rc1.

What did you see?

The generated code for a protobuf message looks as follows:

public final Builder setUnknownFields(
    final com.google.protobuf.UnknownFieldSet unknownFields) {
    return super.setUnknownFieldsProto3(unknownFields);
}

This calls setUnknownFieldsProto3 in GeneratedMessageV3:

protected BuilderType setUnknownFieldsProto3(UnknownFieldSet unknownFields) {
    return this.setUnknownFields(unknownFields);
}

... which then calls the caller setUnknownFields, producing and endless recursion.

This did not happen with version 3.6.1, but using 3.7.0-rc1 breaks our builds:

java.lang.StackOverflowError
at com.company.app.PbAppProtos$MyMessage$Builder.$jacocoInit(PbAppProtos.java)
at com.company.app.PbAppProtos$MyMessage$Builder.setUnknownFields(PbAppProtos.java)
at com.google.protobuf.GeneratedMessageV3$Builder.setUnknownFieldsProto3(GeneratedMessageV3.java:725)
at com.company.app.PbAppProtos$MyMessage$Builder.setUnknownFields(PbAppProtos.java:12366)
at com.company.app.PbAppProtos$MyMessage$Builder.setUnknownFields(PbAppProtos.java:11585)
at com.google.protobuf.GeneratedMessageV3$Builder.setUnknownFieldsProto3(GeneratedMessageV3.java:725)
at com.company.app.PbAppProtos$MyMessage$Builder.setUnknownFields(PbAppProtos.java:12366)
at com.company.app.PbAppProtos$MyMessage$Builder.setUnknownFields(PbAppProtos.java:11585)
at com.google.protobuf.GeneratedMessageV3$Builder.setUnknownFieldsProto3(GeneratedMessageV3.java:725)
at com.company.app.PbAppProtos$MyMessage$Builder.setUnknownFields(PbAppProtos.java:12366)
at com.company.app.PbAppProtos$MyMessage$Builder.setUnknownFields(PbAppProtos.java:11585)
at com.google.protobuf.GeneratedMessageV3$Builder.setUnknownFieldsProto3(GeneratedMessageV3.java:725)
at com.company.app.PbAppProtos$MyMessage$Builder.setUnknownFields(PbAppProtos.java:12366)
at com.company.app.PbAppProtos$MyMessage$Builder.setUnknownFields(PbAppProtos.java:11585)
...

What did you expect to see

... the new rc should be compatible with older generated protobuf files or have a major version change.

[acozzette]

@maja42 Thank you for the bug report. I will make sure we get this fixed in the 3.7.0 release.