[CMake] Could somebody please explain how caching works with NOTFOUND variables?

Brad King brad.king at kitware.com
Thu Oct 19 09:22:27 EDT 2006


Alan W. Irwin wrote:
> I suggest this important additional caching rule concerning the FIND_xxx
> commands should be stated prominently in the principal documentation
> that is
> obtained by running the "cmake --help-full" command.  To be fair, somewhere
> in the Wiki (I have lost the exact reference) I recall there is a specific
> example of the above rule in action, but it wasn't as clearly explained as
> above, and, in any case, I always assumed the Wiki was mistaken (or left
> over from an older version of CMake) since the special rule wasn't
> documented in the principal documentation.

I've updated the docs to include information about when the search is
repeated and when it is not.  I didn't use the exact wording but the
information is there.

Also, note that the commands do not load the variables directly from the
cache and does not treat them specially.  They basically do this:

IF(NOT VAR)
  <try to find something>
  SET(VAR "result of find or <VAR>-NOTFOUND" CACHE <findtype> <docstring>)
ENDIF(NOT VAR)

-Brad


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