Compile Error with 3.21.12 on Ubuntu 23

[Russ White]

Y'all --

When I try to compile on ubuntu 23, I get --

make[1]: Entering directory '/root/frr'
  CXX      grpc/libfrrgrpc_pb_la-frr-northbound.pb.lo
In file included from /usr/include/google/protobuf/stubs/port.h:43,
                 from /usr/include/google/protobuf/stubs/common.h:48,
                 from /usr/include/google/protobuf/io/coded_stream.h:131,
                 from ./grpc/frr-northbound.pb.h:23,
                 from grpc/frr-northbound.pb.cc:4:
/usr/include/google/protobuf/port_def.inc:539:25: error: missing ')' after "__has_attribute"
  539 | #if __has_cpp_attribute(fallthrough)
      |                         ^~~~~~~~~~~
In file included from ./lib/xref.h:13,
                 from ./lib/assert/assert.h:20,
                 from /usr/include/google/protobuf/io/coded_stream.h:113:
/usr/include/google/protobuf/port_def.inc:539:25: error: missing binary operator before token "("
  539 | #if __has_cpp_attribute(fallthrough)
      |                         ^~~~~~~~~~~
In file included from /usr/include/google/protobuf/stubs/stringpiece.h:157,
                 from /usr/include/google/protobuf/stubs/common.h:49:
/usr/include/google/protobuf/port_def.inc:539:25: error: missing ')' after "__has_attribute"
  539 | #if __has_cpp_attribute(fallthrough)
      |                         ^~~~~~~~~~~

This is for the grpc interface on FR Routing ... 

Has anyone seen this before, or have any idea what I need to do here? Maybe there's a breaking change between the version FR Routing is trying to pull in and the most recent version? 

I tried to pull my system down to version 3.12, but I cannot seem to get apt to find the older version in the repositories ...

Any other ideas?

/r