With regards to diagnosing configure, “config.log” is actually a very good record of all the work done by configure. If a check or test fails, config.log shows

With regards to diagnosing configure, “config.log” is actually a very good record of all the work done by configure. If a check or test fails, config.log shows it alongside the exact command line used to compile/link/execute it, allowing you to reproduce a failure (or even just directly see which dependency/local quirk caused it). I’ve found very few reasons to dive into ./configure itself, which as you rightly note is a rats nest.