Serialize and deserialize null (#783)

* Build (grpc's) nanopb with -DPB_FIELD_16BIT

We require (at least) 16 bit fields. (By default, nanopb uses 8 bit
fields, ie allowing up to 256 field tags.)

Also note that this patch adds this to grpc's nanopb, rather than to our
nanopb. We'll need to eventually either:
a) we instruct grpc to use our nanopb
b) we rely on grpc's nanopb instead of using our own.

(^ marked as a TODO for now.)

* Add some dependant protos

Imported from protobuf. Nanopb requires these to be present (though
anything using libprotobuf does not, as these are already built into
that.)

* Add generated nanopb protos based off of newly added proto definitions

* Build the nanopb protos

* Serialize and deserialize null

1 files changed, 9 insertions, 1 deletions

diff --git a/cmake/external/grpc.cmake b/cmake/external/grpc.cmake
index 0af6b31..d545087 100644
--- a/cmake/external/grpc.cmake
+++ b/cmake/external/grpc.cmake
@@ -68,7 +68,15 @@ else()
 
     PREFIX ${PROJECT_BINARY_DIR}/external/grpc
 
-    CMAKE_ARGS ${CMAKE_ARGS}
+    # TODO(rsgowman): We're currently building nanopb twice; once via grpc, and
+    # once via nanopb. The version from grpc is the one that actually ends up
+    # being used. We need to fix this such that either:
+    # a) we instruct grpc to use our nanopb
+    # b) we rely on grpc's nanopb instead of using our own.
+    # For now, we'll pass in the necessary nanopb cflags into grpc. (We require
+    # 16 bit fields. Without explicitly requesting this, nanopb uses 8 bit
+    # fields.)
+    CMAKE_ARGS ${CMAKE_ARGS};-DCMAKE_C_FLAGS=-DPB_FIELD_16BIT;DCMAKE_CXX_FLAGS=-DPB_FIELD_16BIT
 
     BUILD_COMMAND
       ${CMAKE_COMMAND} --build . --target grpc