[cmake-developers] set(CACHE) and the local scope

[Alexander Neundorf]

On Thursday, December 10, 2015 15:26:54 Brad King wrote:
> On 12/10/2015 03:20 PM, Alexander Neundorf wrote:
> >> set(var ON)
> >> option(var "description" OFF)
> >> message("var: ${var}")
> > 
> > I.e. on the first run it would be OFF (since that's the default value
> > of the option), and all later runs it would have the value which is in 
the
> > cache.
> This is calling for the opposite change than Ben's proposal.  Ben
> suggests never unsetting the local value to expose the cached value.
> Alex is suggesting always doing so, even if the cache option is
> not created by the command.
> 
> Alternatively the option() or set(CACHE) commands could also set
> a local variable to the same value as the cache entry.
> 
> This is pretty fundamental behavior so if we are going to mess with
> it through a policy we better get it right.

Yes. :-)

My motivation: if the option() would just set/get the cache variable, and 
leave the local variable untouched, it would be a NOOP in the example 
above, and this is not obvious from seeing that code.

Alex

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