C programing or DRAW it on paper

You are working on a large project. The leader already has the specs for what is needed and is giving to you only what you need to do, other people work on other parts. You need to provide all that is asked exactly as asked, and nothing else.

You are asked to implement functions f1(), f2(), f3() and provide one global variable g, all available to others on the project. You are also asked to provide macro M, also available to others.

In implementing f1() and f2() you decided they two must access a helper global variable g12 (it should not be exposed to others). In implementing f3(), you noticed it was getting long with repeated code so you separated some of the code into a separate helper function f3a() called from f3() as needed. The helper function you just implemented also needs a special macro M1a.

Main is not your responsibility.

Propose architecture for what you are doing. Skip all unnecessary details such as types, interfaces, bodies and calls but show with exact names: all sources, with all headers or variables/macros. For headers, add inclusion prevention.