glslang is included in CMake even if targets already exist

[wrosecrans]

A vulkan application using vkfft may already be using glslang, or depend on some other library that also uses glslang. If multiple places try to add_subdirectory() glslang, then it tries to set up multiple targets with the same name in Cmake's global namespace. So when you add_subdirectory(vkfft), you get errors.

If you wrap the inclusion with something like

if (NOT TARGET OSDependent) add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/glslang-master) endif()

it will be a bit easier to use in some applications.

[DTolm]

Hello,

You don't want to use provided CMakeLists in your app - it has a lot of unnecessary targets like benchmarks and precision verification scripts. A single header nature of VkFFT allows to simply copy it in the application include path and it is good to go (just specify the backend used).

Best regards, Dmitrii Tolmachev