anchor.diff:      main.cpp
       ${PROTO_SRCS}
       ${PROTO_HDRS})
  ----
  +----
   
   This will cause the protobuf compiler to be called when you call `make` on that
   executables target.
  
positive.code: 
  This can be installed on Ubuntu using
  
  ```
  sudo apt-get install protobuf-compiler sudo apt-get install protobuf-compiler
  ```
  
  [[concepts]]
  Concepts
  
negative.code: Generating Source
  ^^^^^^^^^^^^^^^^^
  
  The protobuf CMake package includes a number of helper functions to make the
  code generation easier. In this example we are generating C++ source and use
  the following code:
  
  