code generator protoc-gen-c hasn't been updated to support optional fields in proto3

[flipkickmedia]

What language does this apply to?
C

Describe the problem you are trying to solve.
optional fields in proto3 files using protoc --out_c ...

Describe the solution you'd like
The C version should be listed alongside the other languages to gain support from the OS community

Describe alternatives you've considered
None

[esrauchg]

The Protobuf organization does not have an officially supported C codegen API intended for applications to use.

I suspect you may be with some other code generator owned and implemented by others (of which there are many), but its not clear from the protoc snippet you wrote.