[CMake] functions as first class objects

[Michael Wild]

Something like this just came up recently: http://www.cmake.org/pipermail/cmake/2009-October/032725.html

But probably it would be better to patch the subproject...

Michael

On 13. Nov, 2009, at 5:33 , David Manura wrote:

> Is there a way to redefine a built-in function but still keep around a
> reference to the original function?  Example:
>
>  # wrap "install" function
>  function(install)
>    message("hello!")
>    install(${ARGV})  # original version
>  endfunction()
>
> Unfortunately, in the above case, the "install" inside the function
> refers to the new version of "install", causing an infinite loop.
> There doesn't appear to be a way to save function references either:
>
>  set(old_install ${install})
>  old_install(FILES a DESTINATION b)
>
> Neither can I do tricks like adding a subproject that redefines
> "install" in its own scope.  This still overwrites the "install" in
> the parent project.
>
> ~~~
>
> Now, the original problem I'm trying to solve is that I have project
> maintained by me that does an add_subdirectory on a project maintained
> by someone else.  The subproject does things like
>
>  install(FILES a.pdf DESTINATION share/doc/foo)
>
> but I'd prefer to have its files get stored in my own configurable
> installation locations, without patching the subproject.  This which
> would be possible if the subproject's CMakeLists.txt did something
> like this:
>
>  set(INSTALL_DOC share/doc/foo CACHE PATH "directory for  
> documentation")
>  install(FILES a.pdf DESTINATION ${INSTALL_DOC})
>
> where ${INSTALL_DOC} is a variable that I could redefine in the
> parent.  Another option is if I could simply disable the "install"
> rules in the subproject and redefine my own in the parent project.  I
> could do that via
>
>  function(install)
>  endfunction()
>
> but now how do I restore the original "install" function in order to
> install files in the correct locations?
>
> I also tried temporarily redefining CMAKE_INSTALL_PREFIX to a
> temporary directory, but this variable appears to be evaluated after
> all the "install" commands are processed.
>
> Recursively invoking "CMAKE_COMMAND
> -DCMAKE_INSTALL_PREFIX=${TEMPORARY_FOLDER}" on the subproject may be
> one solution, but I suspect that might be considered harmful.
>
> Maybe I should just patch the subproject. ;)
>