Now that CMake has determined what languages the project needs and has configured its internal infrastructure we can go ahead and write some real CMake code. In practice, very few projects are fully self-contained, as they either depend on external libraries or are themselves libraries that other projects depend on. I really wish that all people upgraded to latest CMake, but the reality is a … Most of this information will be generated by CMake and put in KF5ArchiveTargets.cmake. There’re a lot of interesting thing going on here. This works really nicely since it avoids > explicitly linking my executables and shared libraries with the > dependent libraries of the imported library target. In this article I’m going to talk about building a C++ library with CMake, but it won’t be a CMake tutorial. Here we just told CMake to install our library and to register the target in the export jsonutils-export. 1 The VERSION is a special keyword for this function. Here's the first line of every CMakeLists.txt, which is the required name of the file CMake looks for:. Let’s say you have a C++ library which depends upon a few open source libraries, which have a CMake project structure, but not necessarily done by the book (which means that they get only get built, and not deployed / installed) Below we demonstrate how to download the latest source from the TBB website, and how to use features present in CMake to make sure that the project gets compiled and ready to use in your project. For example, if you specify "native-lib" as the name of your shared library in the build script, CMake creates a file named libnative-lib.so. The key part is add_library(IMPORTED) 2, to tell the library is not generated by CMake system and use the library located outside the project. Here, path-to-example-directory is the path to the directory that contains both CMakeLists.txt and example.cpp. In this post, we'll see a useful way to organize your header only library and generate a CMake target that others can "link" to. If you have multiple installed version of Eigen, you can pick your favorite one by setting the Eigen3_DIR cmake's variable to the respective path containing the Eigen3*.cmake files. Consider for example this sample project A with libraries B and C, where C depends on B. I declared the libraries IMPORTED because the libraries’ own build system consists of a complex mix of Python, CMake and macros which I found difficult to integrate … In CMake, installed targets are registered to exports using the EXPORT argument. GitHub Gist: instantly share code, notes, and snippets. Building a Library with CMake. This could be done in 3 steps: Finding the exact location of libsqlite3.a; Registering it with CMake as an imported library; Adding dl and pthread to the INTERFACE part of its own target_link_libraries() statement. In CMake 3.5, imported targets were added. CMake accounts for these languages when computing how to link a target to the imported library. Then we can go ahead and install the export that we defined above: add_library (libcinder STATIC IMPORTED ) The third argument is the most important here - it tells CMake that this library is pre-built, and that there are therefore no sources to specify. Next, we set the default build type, just in case the user does not specify it. KF5ArchiveConfigVersion.cmake (generated by ecm_setup_version above) will allow find_package(KF5Archive 5.12.0) to determine whether this is a compatible library version. I also wonder if NAMESPACE is valid for IMPORTED targets in cmake 2.8.12. Introduction to the basics Minimum Version. AFAICS, you've a single imported target GTest, and you are continuously setting *this* target's location - sometimes for a debug configuration, sometimes without configuration - to the location of its *prerequisite* libraries reported by the GTest package's find module or config file. Update: now using modern cmake (version >= 3.9), since commit 46f0b93. CMake library example that can be found using find_package(). This target populates the appropriate usage requirements for INTERFACE_INCLUDE_DIRECTORIES to point to the appropriate include directories and INTERFACE_COMPILE_FEATURES for the necessary C++11 flags.. External¶. TBB is a C++ library, hence our example will be with C++ source. The first example could’ve been better with a version number such as 1.2.3 rather than 0.0.0. Pass the name of the library target to target_link_libraries to use the respective library. Qt6Widgets_FOUND: A boolean that describes whether the module was found successfully. One last way to improve this example would be to tell CMake that the libsqlite3.a library also needs dl and pthread. The command name cmake_minimum_required is case insensitive, so the common practice is to use lower case. You can also use the nlohmann_json::nlohmann_json interface target in CMake. For example, when a C executable links to an imported C++ static library CMake chooses the C++ linker to satisfy language runtime dependencies of the static library. With IMPORTED_LOCATION and INTERFACE_INCLUDE_DIRECTORIES, CMake can detect where the library (.a or .so) and headers (.h) are. It knows that because Qt5::Widgets is a target defined in files shipped by Qt in the lib/cmake directory. The long answer is a bit more complicated. Since you are copying the library files directly to the devel and install spaces, why do you need to create a CMAKE target for the imported library? Basic CMake, part 2: libraries By Martin Hořeňovský Jun 2nd 2018 Tags: CMake, Tutorial, C++. The main advantage of this example is that it is auto-generated. This works faster as referencing the library project’s directory using the add_subdirectory() command, as the exporting mechanism allows precisely selecting which targets to export. Mitch Woodside ( 2020-01-06 17:50:42 -0600) edit. To use this library from a CMake project, you can locate it directly with find_package() and … You only need to change the project name, and add the files that need to be compiled in foo/CMakeLists.txt. This tutorial shows how to export a CMake library to a package and import it from a different project using the find_package() command. The target names start with Qt6::, followed by the module name.For example: Qt6::Core, Qt6::Gui.Pass the name of the library target to target_link_libraries to use the respective library.. Each Qt module that is loaded defines a CMake library target. All of the sudden I found myself in a situation that I have been successfully avoiding so far - I needed to make a C++ library with CMake. Also, INTERFACE was introduced (at least for add_library()) in cmake 3.0, this is the type of things we must be careful about. Qt6Widgets_LIBRARIES: The name of the imported target for the module: Qt5::Widgets CMake¶. A string of flags to use when building executables against the library. Also define a my_library-config-version.cmake.in similar to above for version compatiblity checks. CMake is aware that using the Qt5::Widgets library involves a compilation step and a linking step. Linux/UNIX developers are often surprised to learn that creating a shared library on Windows known as a DLL (dynamic linked library) requires changes to the source code or an explicit listing of all the symbols that the dll will export. Because I did not specify SHARED, CMake automatically created a static library.You can influence this default behavior by setting the BUILD_SHARED_LIBS variable, for example, as an option for your library users. Even if the libraries are not installed, CMake makes it easy to use them: you copy the library into a folder in the project source tree (or use Git Submodules or whatever) and then use add_subdirectories to include the project. These files tell CMake that Qt5::Widgets is a SHARED library, and that it has been IMPORTED for use from upstream. Re: “Both these properties control “Technical parts” and should be looked at from a technical perspective. Add_library CMake example. IMO, this doesn't make any sense. Once you’ve defined the library, you then have to tell CMake where the prebuilt library is located. Example cmake for windows including auto copy dll. Define a file named my_library-config.cmake that just includes the corresponding my_library.cmake file (see above, just copy-paste that). For instance: One of the important changes in Visual Studio 2017 for native development is support for CMake. Imported library targets. If a library does not export any symbols, it must not be declared as a SHARED library. Qt6Widgets_INCLUDE_DIRS: A list of include directories to use when building against the library. Features. Long Explanation. For example, a Windows resource DLL or a managed C++/CLI DLL that Instead other targets created by add_library or add_executable may reference the objects using an expression of the form $ as a source, where objlib is the object library name. We will make use of CMake's INTERFACE library feature to do this: An INTERFACE library target does not directly create build output, though it may have properties set on it and it may be installed, exported and imported. The target names start with Qt5::, followed by the module name. Download demo sources - 4.7 KB; Introduction. Note: The targets are also available with a Qt:: prefix: Qt::Core, Qt::Gui, and so on.See also Qt 5 and Qt 6 compatibility. > I am using the nice feature of exporting targets from one CMake > project to another. CMake has a module called ExternalProject that can do this for you. However, CMake has the dependency information baked into it for all known versions of Boost, so CMake must be newer than Boost for these to work. KF5ArchiveConfig.cmake will provide all the information necessary to actually use KArchive. Exports are therefore just a set of targets that can be exported and installed. Note that in this example ${PROJECT_NAME} and "foo" must be the same name, since we are using ${PROJECT_NAME} as the name of the library. In the first command, BUILD_SHARED_LIBS is read by CMake to switch between static and shared library, and a user could alter this option in cache. cmake-example-library. Hello, My CMake project uses some third party libraries which I declared as IMPORTED then I set the IMPORTED_IMPLIB or IMPORTED_LOCATION properties (depending on compiler and type of library) to the full path and file name. Story-time CMake Default Behavior. The first thing that everybody does when learning CMake is write a toy example like this one that generates a single executable. add_library, If a library does not export any symbols, it must not be declared as a SHARED library. This is because CMake expects a SHARED library to always have an associated import library on Windows. For example: Qt5::Core, Qt5::Gui. Example of CMake easy libraries. David Robillard says: 2014-07-09 at 21:20. The convention CMake uses to name the file of your library is as follows: liblibrary-name.so. Let's mention a bit of CMake syntax. 3 comments on “ CMake and library properties ” Syam says: 2014-07-09 at 17:39. CMake is a cross-platform open-source tool for defining the build process for native applications independently of compilers and environments. CMake 3.4 will have a new feature to simplify porting C and C++ software using shared libraries from Linux/UNIX to Windows. For example, a Windows resource DLL or a managed C++/CLI DLL that exports no unmanaged symbols would need to be a MODULE library. First, we need to tell CMake the library name, version and language. Each Qt module that is loaded defines a CMake library target. Well, the generate_export_header command creates a header file which helps switch between building shared and static libraries. To clarify, this will be about so-called normal kind of library. cmake_minimum_required (VERSION 3.1) . GitHub Gist: instantly share code, notes, and snippets. My previous post about CMake provided a simple CMakeLists.txt for a small, self-contained, project. These targets handle dependencies for you as well, so they are a very nice way to add Boost libraries.