[CMake] Can an option enforce a default, even if cache is present?

[Eric Noulard]

Le mar. 27 nov. 2018 à 14:50, Mario Emmenlauer <mario at emmenlauer.de> a
écrit :

>
> Dear all,
>
> I've just discovered that option() behaves differently than I anticipated.
> After reading the docs and searching with google I'm still confused how to
> achieve my desired behaviour.
>
> What I've just learned is that unspecified options take their cached value
> and do *not* go back to their default value, if a cache exists. I assumed
> that options take their default when not explicitly specified.
>

The behavior of option() gained new behavior in CMake 3.13.
May be it could help in your particular case:
https://cmake.org/cmake/help/v3.13/policy/CMP0077.html#policy:CMP0077

you'll depend on latest CMake though.


>
> Now my problem: I could not find a way to get the behaviour I'd like. Is it
> possible to enforce the default for an option when its not specified by the
> user, even if a cache exists?
>

You mean you did not manage to force the cache value?
You can:
set(VAR "default_value" CACHE FORCE)

or the problem is you cannot know whether if a value has been user-provided?


> I tried to unset() the option from the cache but that does not do what I'd
> like.
>
> All the best,
>
>     Mario Emmenlauer
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-- 
Eric
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