[CMake] Are the [Project name]_SOURCE_DIR variables stored in the cache ?

[Glenn Coombs]

Ugh !  It gets messier.  I'm beginning to understand why it is the way it
is.  The cmake developers have probably already been round this loop and
decided it wasn't worth the effort :-)


On 1 May 2014 19:41, Nils Gladitz <nilsgladitz at gmail.com> wrote:

> On 01.05.2014 20:38, Glenn Coombs wrote:
>
>> Okay, I think I understand what you're saying.  Variables set in a
>> CMakeLists.txt file added by add_subdirectory are only visible in that
>> CMakeLists.txt and any further ones it adds via add_subdirectory.  The
>> higher level CMakeLists.txt files would not have the necessary visibility,
>> hence the need to cache the project source directory variable.  To make it
>> behave consistently it would be necessary for cmake to be able to set a
>> variable in the scope of the top level CMakeLists.txt.  Similar to the
>> PARENT_SCOPE that the set() command already has, something like
>> set(foo_SOURCE_PROJECT "path/to/source" ROOT_SCOPE).
>>
>> I suspect that the reason cmake is caching these variable is because the
>> set() command doesn't have a ROOT_SCOPE ability and using cache variables
>> was the easiest way to simulate that.  And we have to live with the
>> unfortunate side effect that the cached variables don't exist on the first
>> run but do on subsequent runs.
>>
>>
> I don't think it would be sufficient to set it in the root scope either
> since I think each scope has its own copy of the variable.
> It would have to be set for all scopes between the root and the current
> scope.
>
> Nils
>
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