1/10/2023 0 Comments Cmake commandsWhen CMake processes the above, here is what occurs: One may naively expect the output to be as follows: Hello from thirdīut instead, the first implementation is never called because the second one ends up calling itself in an infinite loop. This has the potential to lead to infinite recursion, as the following contrived example demonstrates: function(printme) The prepending of one underscore to “save” the previous command only applies to the current name, it is not applied recursively to all previous overrides. If a command is only ever overridden once, techniques like in the example above appear to work, but if the command is overridden again, then the original command is no longer accessible. This applies whether the old name is for a built-in command, a custom function or a macro. When function() or macro() is called to define a new command, if a command already exists with that name, the undocumented CMake behavior is to make the old command available using the same name except with an underscore prepended. (The following explanation is largely extracted from the Functions And Macros chapter of the book Professional CMake: A Practical Guide) It relies on undocumented behavior to call through to the original implementation using _find_package(). Otherwise, the call should be forwarded to the original built-in find_package() command. If it is in that list, then it should be assumed that the package will be added to the project directly via add_subdirectory() and the find_package() call should do nothing. The intent behind the above block of CMake code is to redefine the built-in find_package() command such that it checks if the package to be found is one of those named in the as_subproject list variable. In the section of the talk where package management is discussed, the following example code is presented (around 52m38s): set(CMAKE_PREFIX_PATH "/prefix") The example in question relies on undocumented behavior, the dangers of which may not be immediately obvious and can lead to infinite recursion. The source code of this sample project canbe found at CMakeLists.txt and test.In this article, we take a closer look at a particular example from the popular Effective CMake talk by Dan Pfeifer. The first command will creates CMake configuration files inside folder build and the second one will generate the output program hello in bin folder. To build your project hello, just do $ cmake -H. At this point, you will have the folder with the following files: $ ls Now, let build the source code with CMake. # Set the output folder where your program will be created test.cpp # include using namespace std Īnd you saved it as test.cpp, then to compile it in CMake you should create a txt file named CMakeLists.txt # Specify the minimum version for CMake CMake will do the job of Makefile from now. So I assume that you know C++ and what the Makefile is. To install CMake in Linux, just simply do on your terminal # For Ubuntu If you have some troubles with gcc and Makefile, just move out to CMake. In a short conclusion, CMake help you to manage and build your source codes effectively. This information is gathered into the cache, which may be changed by the user prior to the generation of the native build files. For example, when CMake runs, it locates include files, libraries, and executables, and may encounter optional build directives. Another nice feature of CMake is that it generates a cache file that is designed to be used with a graphical editor. CMake also supports static and dynamic library builds. CMake supports in-place and out-of-place builds, and can therefore support multiple builds from a single source tree. CMake can generate a native build environment that will compile source code, create libraries, generate wrappers and build executables in arbitrary combinations. Simple configuration files placed in each source directory (called CMakeLists.txt files) are used to generate standard build files (e.g., makefiles on Unix and projects/workspaces in Windows MSVC) which are used in the usual way. Unlike many cross-platform systems, CMake is designed to be used in conjunction with the native build environment. What is CMake?ĬMake is an extensible, open-source system that manages the build process in an operating system and in a compiler-independent manner.
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