[CMake] How to find a work arround with CMP0026 policy

[Nils Gladitz]

On 30.07.2014 17:41, Fabien Spindler wrote:
> Hi,
>
> I'm not able to find a good way to modify my cmake files to consider 
> CMP0026 policy introduced in cmake 3.0.0.
>
> I have a project that create a library libfoo and FooConfig.cmake file 
> that allows to use my library as a 3rd party.
> In FooConfig.cmake updated during configuration time, I need to set 
> FOO_LIBRARIES with the full path and name of the library in debug and 
> release. To get the library names, I use the target location property. 
> Since cmake 3.0.0 this seems a bad idea.
>
> CMake Warning (dev) at CMakeLists.txt:8 (get_target_property):
>   Policy CMP0026 is not set: Disallow use of the LOCATION target property.
> CMake Warning (dev) at CMakeLists.txt:9 (get_target_property):
>   Policy CMP0026 is not set: Disallow use of the LOCATION target property.
>
> Here is a small example that reproduces the behavior.
>
> -- Begin CMakeLists.txt --
> project(test)
> cmake_minimum_required(VERSION  2.6)
> add_library(foo  foo.cpp)
> get_target_property(FOO_LIBNAME_DBG  foo  LOCATION_Debug)
> get_target_property(FOO_LIBNAME_OPT  foo  LOCATION_Release)
> get_filename_component(FOO_LIBNAME_DBG  "${FOO_LIBNAME_DBG}"  NAME)
> get_filename_component(FOO_LIBNAME_OPT  "${FOO_LIBNAME_OPT}"  NAME)
> configure_file(FooConfig.cmake.in  FooConfig.cmake)
> -- End CMakeLists.txt --
>
> -- Begin FooConfig.cmake.in --
> set(FOO_SOURCE_DIR  @CMAKE_SOURCE_DIR@)
> set(FOO_LIBNAME_DBG  "@FOO_LIBNAME_DBG@")
> set(FOO_LIBNAME_OPT  "@FOO_LIBNAME_OPT@")
> set(FOO_LIBRARIES  debug  @CMAKE_INSTALL_PREFIX@/lib/${FOO_LIBNAME_DBG}  optimized  @CMAKE_INSTALL_PREFIX@/lib/${FOO_LIBNAME_OPT})
> -- End FooConfig.cmake.in --
>
> Adding the following lines in my CMakeLists.txt seems not the best way 
> to ensure compat with future versions of CMake.
>
> if(POLICY  CMP0026)
>    cmake_policy(SET  CMP0026  OLD)
> endif()
>
> I tried also to play with add_custom_command() using
> $<TARGET_PROPERTY:foo,LOCATION_Debug>
> But I cand find any command that set a variable
>
> Any idea ?
>
> Thanks
> Fabien

You could use file(GENERATE) [1] with the TARGET_FILE (_NAME, _DIR) [2] 
generator expressions (one file per configuration).

Or use export() [3] to export your targets for use in your build 
directory package configuration file.
You could then add those targets to FOO_LIBRARIES instead of the full paths.

[1] http://www.cmake.org/cmake/help/v3.0/command/file.html
[2] 
http://www.cmake.org/cmake/help/v3.0/manual/cmake-generator-expressions.7.html#informational-expressions
[3] http://www.cmake.org/cmake/help/v3.0/command/export.html
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