[cmake-developers] unset and cache variables

Robert Maynard robert.maynard at kitware.com
Thu Aug 16 17:46:33 EDT 2018


Looking at the current docs (
https://cmake.org/cmake/help/v3.12/command/unset.html ) I think the
first paragraph needs to be read as a single statement to understand
the behavior.

"Removes the specified variable causing it to become undefined. If
CACHE is present then the variable is removed from the cache instead
of the current scope."

I think we can be more explicit by rephrasing as:

"Makes the local variable variable from the current scope be
undefined, If CACHE is present then instead the cache variable is
undefined."
On Thu, Aug 16, 2018 at 5:38 PM James Touton <bekenn at gmail.com> wrote:
>
> I just recently came across this:
>
> set(BLAH blah CACHE INTERNAL "")
> unset(BLAH)
> message("BLAH: ${BLAH}")
>
> Surprisingly (to me), this prints out "blah".  I had expected the unset command to make the cached value inaccessible.  The documentation just states that the function "[r]emoves the specified variable causing it to become undefined."  Is this a bug?  I would prefer for the function to guarantee that ${BLAH} comes up empty.
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