It is not clear if was Knuth or Hoare who coined the phrase:
We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil.
It is indeed very true. I would like to add a humble corollary:
premature bugfixing is lame too.
So, here is my advice: Sleep your bugs.
I am not talking about typos. You know, misspelling 'l' and '1' for example (nobody should use 'le0' as var name, '1e0' is still a valid number) or failing to include a range check (last time I forget to place an 'if' I got a Pwnie nomination)
I am talking about logic bugs. Something wrong with the algorithm or the true logic of the program. Adding inconsistent features is another example.
Sleep those kind of bugs. Take good note of them, and wait a day or two in fixing. Probably you will find a neat way to deal with the issue without changing those hundreds of lines. Maybe not, but even in this case the solution is worth of the wait.
In my case the bug was black point detection. lcms2 is now an unbounded CMM that operates on floats. So the black point detection code was using floating point to do the calculations. Yep, it seems a nice feature: far more precision, etc. On the other hand, inks on floating point are represented as %, so the effective range is 0..100%, that is how Photoshop and others do work and I thought it makes sense to keep the feature in lcms2 as well.
Put both features together and you have a nice logic bug: extra code is needed on BP detection to deal with different ranges.
If you happen to be a professional programmer, you surely realize that my advice of postpone bug fixing goes against the schedule, the program manager and the planner. Sure, but that's lcms2, my pet project which has unlimited resources on time. Would be a dream for a commercial project, but this project is not commercial and therefore is not subjected to schedule tyranny.
By the way, a new drop of lcms2 is in the way and will be available in a day or two.