[CMake] Problem while setting variables in CMakeCache

[Stefan Köhnen]

2010/9/7 James Bigler <jamesbigler at gmail.com>:
> 2010/9/7 Stefan Köhnen <stefan.khnen at googlemail.com>:
>> 2010/9/6 Alexander Neundorf <a.neundorf-work at gmx.net>:
>>> On Monday 06 September 2010, Stefan Köhnen wrote:
>>>> Ah, okay.
>>>>
>>>> Thanks for your fast reply.
>>>>
>>>> Is there a way to change the value in the cache?
>>>
>>> set(... FORCE)
>>>
>>> Alex
>>>
>>
>> Hello Alex,
>>
>> thanks again for your reply. I tried to use set with FORCE but it didn't work.
>>
>> My CMakeLists.txt looks like this:
>>
>> PROJECT(CMakeTest)
>>
>> SET(VAR_FOR_TEST "firstValue" CACHE STRING "Just for testing")
>>
>> set(VAR_FOR_TEST "secondValue" FORCE)
>
> This second command also needs to set the cache value:
>
> set(VAR_FOR_TEST "secondValue" CACHE STRING "Just for testing" FORCE)
>
> Keep in mind, that this will prevent the user from changing this value
> from the GUI, since you are forcing it.
>
> An alternative that I've employed with FindCUDA is to set the variable
> *before* calling find_package(CUDA).
>
> set(VAR_FOR_TEST "secondValue" CACHE STRING "Just for testing" FORCE)
> find_package(CUDA)
>
> The first set(CACHE) command wins and the one in the FindCUDA script
> doesn't take effect.
>
> A second alternative that I've employed is to keep a flag called
> PASSED_FIRST_CONFIGURE that is set to ON at the end of the top level
> CMakeLists.txt file:
>
> set(PASSED_FIRST_CONFIGURE ON CACHE INTERNAL "Already Configured once?")
>
> During execution of the CMake scripts, I can check for this flag and
> only do set(CACHE FORCE) commands if PASSED_FIRST_CONFIGURE evaluates
> to false:
>
> if(NOT PASSED_FIRST_CONFIGURE)
>  set(flag "--use_fast_math")
>  list(FIND CUDA_NVCC_FLAGS ${flag} index)
>  if(index EQUAL -1)
>    list(APPEND CUDA_NVCC_FLAGS ${flag})
>    set(CUDA_NVCC_FLAGS ${CUDA_NVCC_FLAGS} CACHE LIST "Semi-colon
> delimit multiple arguments." FORCE)
>  endif()
> endif()
>
> James
>

Hello James,

thanks for your reply, I implemented your first suggestion and this
works perfectly.

I think your idea with PASSED_FIRST_CONFIGURE flag is propably the
most flexible way to implement this, maybe we will use something
similar to allow changes from the GUI.

Stefan