change log level per rt-app invocation

[v0lker]

currently, it is a compile-time option which i find a bit tedious. could have a command line flag (how about -l ?). i'm assuming that the overhead is acceptable. could provide a PR, if this feature isn't disliked - ?

[jlelli]

It might be handy. Maybe just follow the -v -vv -vvv common pattern?
Also maybe keep a config option to completely disable logging? Just in case overhead is found not to be so negligible.

[v0lker]

-v is already taken for 'version', so i'd rather leave it in peace. any other suggestion?

as for the overhead and completely disabling:
going from setting the debug level at compile time to doing it dynamically, we'd incur the overhead of an integer comparison for every log_*() invocation. the branch predictor should be very effective here (i think) as the result is always the same.

right now i can think of only one way to have even less overhead and still log dynamically: rewriting the log function in the process' .text in memory on start-up (replacing the function calls with nops). i don't think it is worth the effort, though.

what would you suggest?

[jlelli]

OK. Please go for -l --log and don't worry about the overhead. We will figure it out later if it turns out to be a real problem, I guess.

[v0lker]

remaining task is to allow a string instead of the numerical value for the -l option. i'll provide a PR soon, unless someone else is eager...

[v0lker]

#68 implements the remaining issue