Emitting errors


In a project, you can fail in several ways:
Fail at build time (compilation error)
Fail at init time (early run-time)
Fail at run-time
Misbehave with no hard failure

A build failure is to be preferred, whenever possible
You save a lot of time if you error out early

How to fail at  build time
Complain with #warning/#error (on condition)
Overflow ram/stack at build time (on mishap)
Refer to an undefined symbol (on condition)
Create an array of negative size (on condition)

 #define BUILD_BUG_ON(condition)
        ((void)sizeof(char[1 - 2*!!(condition)]))