cmake-library

Template of CMake files to build a static or shared library under Windows and Linux.

Needs of CMake 3.23:

• TARGET_RUNTIME_DLLS lists all dynamic libraries (Windows only) dependencies of an executable. These DLL will be copy in the same path than the executable. Needs CMake 3.21.
• FILE_SET HEADER to install header like PUBLIC_HEADERS. This new feature keeps tree path. The old solution is to install DIRECTORY include/ but guidelines recommand to use explicit file and avoid wildcard. Needs CMake 3.23.

If you can't use latest CMake, you may have a look at cxx-static-shared-example. It's another example with a branch for CMake 3.8 and CMake 3.12.

Use cases

The goal of this template is to support the worst case.

There is a main library: library

Then two libraries depend on library: library2, library3.

And a final library library4 that depends on library2 and library3. It's a diamond dependency.

After, a simple executable extern is linked with library4.

CMakeLists.txt

All interesting data in this POC are in CMakeLists.txt files in library folder. There is also comment about BUILD_FETCH_CONTENT in lib/CmakeLists.txt for library2. The other folders are just a clone of the main folder to show that everything is working well for the worst scenario.

You need to know the basics of CMake. The whole official tutorial is perfect.

The content in C++ source files is very simple.

To know how to build this example, simply follow instruction in .github\workflows\cmake.yml file.

Typical problems this project handle

When using shared library, you need to define symbol library_Export when building library and undefining it when linking the library. It's automatically done when calling add_library in SHARED mode.

Under Windows with shared library, you need to copy all libraries in the same folder than the executable. TARGET_RUNTIME_DLLS generator-expression will help.

Diamond dependency doesn't look to be a problem with this example.

Don't explicitly (on user side) depends on library when linking library2 or library3. But you need to explicitly do it in Config.cmake file.

Libraries can be built with FetchContent or find_package. Simply set BUILD_FETCH_CONTENT option.

Fix-me

Don't set CMAKE_INSTALL_RPATH and CMAKE_INSTALL_RPATH_USE_LINK_PATH in CMakeLists.txt. But without it, CI doesn't pass.