CMake Error: Cannot determine link language for target

Question

I created the following Directory:

FrameWork/
├── CMakeLists.txt ==> contains only add_subdirectory(UtilsBasic)
└── UtilsBasic
    ├── CMakeLists.txt ==> Contains only add_subdirectory(SmartSingleton)
    └── SmartSingleton
        ├── CMakeLists.txt
        ├── include
        │   └── SmartSingleton.hpp

---

The CMakeLists.txt in SmartSingleton directory contains:

set(codeprod_list
        include/SmartSingleton.hpp)

USR_add_shared_lib(SmartSingleton "${codeprod_list}")
target_link_libraries(SmartSingleton PUBLIC Common)
target_include_directories(SmartSingleton PUBLIC include/)

---

The main CMakeLists.txt of the project is the following:

cmake_minimum_required (VERSION 3.4)

project (MyProject)
USR_init_project(MyProject)

add_subdirectory(src/FrameWork)

---

Error

-- Configuring done CMake Error: CMake can not determine linker language for target: SmartSingleton CMake Error: Cannot determine link language for target "SmartSingleton".

I don't understand Why I am getting that Error. I mean In the Framework I created a link to UtilsBasic and in turn a link to SmartSingleton.

Answer 1

Try this in your SmartSingleton/CMakeLists.txt file:

set_target_properties(SmartSingleton PROPERTIES LINKER_LANGUAGE CXX)

This will directly tell CMake which language to use for that target.

If your library is truly only header files though, you will likely receive the error you mention also. Consider making this library an INTERFACE library:

add_library(SmartSingleton INTERFACE)
target_include_directories(SmartSingleton INTERFACE include/)

Here are the docs for INTERFACE libraries.