[CMake] Feature wish - constrained string values for configuration options

[Alexander Neundorf]

On Thursday 24 July 2008, Robert Haines wrote:
> On 18 Jul 2008, at 18:40, Bill Hoffman wrote:
...
> > However, it is not that easy to implement, since the basic type in
> > CMake is a string.  There is no way to constrain the value of a
> > variable, or even store more information about a variable.
>
> I decided to knock something up using macros that does what I need. It
> obviously doesn't constrain choices in a UI or provide a drop down
> menu but it does raise an error if the user tries to configure a
> project with a value set outside of a list of allowed values. It does
> enough for me for now and hopefully someone else will find it useful.
>
> There are two versions. My first attempt needs you to define your
> variable first:
> set(TEST_OPT "None" CACHE STRING "Some Documentation")
> then call the assert_option macro like this:
> assert_option(${TEST_OPT} "TEST_OPT" "None, One, Two, Three")
>
> But I felt that was a little ungainly so my second attempt is called
> like this (without a prior "set"):
> select_option(VARIABLE INITIAL-VALUE ALLOWED-VALUE-LIST DOCUMENTATION)
> example:
> select_option(TEST_OPT "None" "None, One, Two, Three" "Some
> Documentation")
>
> You can grab it straight from my git repository here:
> http://git.kato.mvc.mcc.ac.uk/zzcgurh/option-macros.git/
>
> If you just want a tarball use the "snapshot" link on that page - you
> want the line with the yellow "v-1.0" tag on it.
>
> Once you've got it (and un-tarred it) you can just point ccmake at the
> directory as it has a full top-level CMakeLists.txt which uses both
> forms of the macro.

The problem with that is that you can still set the variable to different 
values afterwards, and I guess this is what Bill means with "there is no way 
to constrain the value".

So I guess it's not good enough as a generic solution for cmake :-/

Alex