CMake Library Configuration File: Linking Debug and Release Version of a Library

CMake Library Configuration File: Linking Debug and Release Version Library

In this article, we will discuss how to create a CMake library configuration file that links the debug and release version of a library. This is particularly useful when building and distributing libraries for other developers to use. We will cover the key concepts of CMake library configuration files, with detailed explanations and subtitles.

What is a CMake Library Configuration File?

A CMake library configuration file, typically named [library_name]-config.cmake, is a script that provides information to other projects about how to link against a library. It contains instructions for finding the library's include directories, libraries, and other properties needed to use the library.

Why Create a Library Configuration File?

Creating a library configuration file makes it easy for other developers to use your library. They no longer need to manually specify the include directories, libraries, and other properties; instead, they can simply include the configuration file, and CMake will handle the rest.

Linking Debug and Release Versions of a Library

When linking a library, it's important to link against the correct version of the library. For example, when building a project in debug mode, you should link against the debug version of the library; when building in release mode, you should link against the release version.

Creating the Library Configuration File

To create a library configuration file that links the debug and release version of a library, you can follow these steps:

1. Create a variable that contains the name of the library.
2. Create another variable that contains the name of the debug library.
3. Create a third variable that contains the name of the release library.
4. Set the IMPORTED_LOCATION_DEBUG and IMPORTED_LOCATION_RELEASE properties of the library target to the full path to the debug and release libraries respectively.
5. Set the IMPORTED_LINK_INTERFACE_LANGUAGES property of the library target to the programming language(s) used by the library.
6. Set the IMPORTED_LINK_INTERFACE_LIBRARIES property of the library target to any other libraries that the library depends on.
7. Provide a helper macro that other projects can use to link against the library.

Example Library Configuration File

Here's an example library configuration file that links the debug and release version of a library called my_library:

set(my_library_NAME my_library)
set(my_library_DEBUG_NAME ${my_library_NAME}d)
set(my_library_RELEASE_NAME ${my_library_NAME})

set_target_properties(${my_library_NAME} PROPERTIES
  IMPORTED_LOCATION_DEBUG "${CMAKE_CURRENT_LIST_DIR}/lib/${my_library_DEBUG_NAME}.so"
  IMPORTED_LOCATION_RELEASE "${CMAKE_CURRENT_LIST_DIR}/lib/${my_library_RELEASE_NAME}.so"
  IMPORTED_LINK_INTERFACE_LANGUAGES "CXX"
  IMPORTED_LINK_INTERFACE_LIBRARIES "thread")

include(FindPackageHandleStandardArgs)

find_package_handle_standard_args(${my_library_NAME} REQUIRED_VARS ${my_library_NAME}_LIBRARY)

if(${my_library_NAME}_FOUND)
  if(NOT TARGET ${my_library_NAME})
    add_library(${my_library_NAME} UNKNOWN IMPORTED)
    set_target_properties(${my_library_NAME} PROPERTIES
      IMPORTED_LOCATION_DEBUG "${CMAKE_CURRENT_LIST_DIR}/lib/${my_library_DEBUG_NAME}.so"
      IMPORTED_LOCATION_RELEASE "${CMAKE_CURRENT_LIST_DIR}/lib/${my_library_RELEASE_NAME}.so"
      IMPORTED_LINK_INTERFACE_LANGUAGES "CXX"
      IMPORTED_LINK_INTERFACE_LIBRARIES "thread")
  endif()
else()
  if(TARGET ${my_library_NAME})
    remove_target(${my_library_NAME})
  endif()
endif()

mark_as_advanced(${my_library_NAME}_LIBRARY)

Using the Library Configuration File

To use the library configuration file in another project, you can follow these steps:

1. Include the library configuration file using the find_package() command.
2. Use the helper macro to link against the library.

Example Project File

Here's an example project file that uses the library configuration file we created earlier:

cmake_minimum_required(VERSION 3.10)
project(example)

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

find_package(my_library REQUIRED)

add_executable(example main.cpp)
target_link_libraries(example ${my_library_NAME})

• A CMake library configuration file provides information to other projects about how to link against a library.
• Linking the debug and release version of a library is important for building and distributing libraries for other developers to use.
• Setting the IMPORTED_LOCATION_DEBUG and IMPORTED_LOCATION_RELEASE properties of the library target allows you to link against the correct version of the library.
• Providing a helper macro that other projects can use to link against the library makes it easy to use.

References

• find_package()
• add_library()
• IMPORTED_LINK_INTERFACE_LANGUAGES
• IMPORTED_LINK_INTERFACE_LIBRARIES