Failing at run time


A run-time failure is worse than a build-time failure
You need to install and run the binary to just fail...

Failing at init time is preferred
... if you are unable to fail al build time
Init time is not performance-critical *at all*
If RAM/flash allows, please be verbose in your messages

Sometimes you can trust your caller and avoid checks
For example, gpio_set/gpio_get, after checking at init time
Or you can offer the double API:
__some_function() doesn't check
some_function() checks arguments, and is slower

Any "assert" or "panic" in a critical path is a cost
Assertions can be a build-time option
Or you can think about a faster way to do BUG()