Suppose we have application on Linux, pure C. Application consists of several functions - `f1`, `f2` and `f3`, which receive a structure. One element of the structure is `debug_mode`, with values `ON` or `OFF`.

How can I switch debug mode in `f1`, `f2` and `f3` (for example, some `printf`s) when the structure has `debug_mode == ON`?

Should I always use `if` statements to check `debug_mode` for every incoming structure or there is some another best practise to not use always `if` statements?

For example, these could be traces in telecom products, where we could collect some trace data for a specified subscriber.