[CMake] How to debug a CMake script?

[Christoph Grüninger]

Hi CMake,
how do you debug CMake scripts? I know -Wdev, --debug-output, 
and --trace but often they are not sufficient. If I am
interested in the value of a variable or want to check why a
test fails I have no clue what to do. Currently, I work with
printf debugging, a technique from the middle age of computer
programming.
Does a special mode or program exist to help me with debugging?
How do you do your debugging?

Thanks in advance,
Christoph

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I don't like that.                     [Sheldon, S03E13]