[CMake] CMAKE_SYSTEM not available

[Philip Lowman]

On Wed, Sep 30, 2009 at 5:24 AM, Martin Apel <martin.apel at simpack.de> wrote:

>  I had a similar issue with CMAKE_SYSTEM_NAME. I have put platform specific
> default settings into files called "Linux.cmake" and "Windows.cmake",
> where the file is included as
>   INCLUDE (${CMAKE_SYSTEM_NAME}.cmake)
>
> However it's not possible to initialize some variables, because this
> include statement has to be after the PROJECT command.
> I tried to set CMAKE_EXE_LINKER_FLAGS_INIT inside these platform-specific
> files, but it seems that it's too late to set them after
> the PROJECT command. So I have a cycle:
> - I cannot use the above include statement before the PROJECT call
> - but if I use it after the PROJECT call I cannot set some variables
> anymore (I can set them, but they have no effect, because in the above
> example
>   CMAKE_EXE_LINKER_FLAGS is initialized from CMAKE_EXE_LINKER_FLAGS_INIT
> during the PROJECT call)
>
> Currently I work around this by not setting CMAKE_EXE_LINKER_FLAGS_INIT,
> but CMAKE_EXE_LINKER_FLAGS inside my Linux.cmake. This used to work fine
> with CMake 2.6, but 2.8 issues a warning, that I am overwriting a cached
> variable.
>
> What is the recommended way to initialize platform-specific flags, which
> are held in the cache?
>

You are correct that conditionals don't work prior to project() in the
toplevel file but they seem to work fine within the platform override .cmake
file itself.  You might try having one flags file with whatever conditionals
you need for Linux, Windows, etc.

For example:
http://www.cmake.org/Wiki/CMake_FAQ#Make_Override_Files

-- 
Philip Lowman
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