![]() If those are empty, it will look for cc and c++ executables in the PATH. It checks the CC and CXX environment variables for the C and C++ compilers, respectively. On all generators, CMake sniffs the environment for which compiler to use. You can also set to ClangCL to use the Visual Studio provided ClangCL tools. Typically, you will want this to be host=圆4 to ensure that 64-bit MSVC is used, which can allocate more memory for large linking steps. If is not specified, then the 32-bit MSVC compiler will be used. Valid values of include Win32, 圆4, ARM, and ARM64. The full form of the CMake configure command for this is: $ cmake -G "Visual Studio 16 2019" -A -T When using the Visual Studio generators specifically, you can tell CMake which platform you wish to target and which version of the compiler you would like to use. Check the project's documentation to see which options are available. This particular variable is a convention, but is not guaranteed to be honored. For example, a common way to disable building tests is to set BUILD_TESTING to NO at the command line: $ cmake -S /path/to/source-dir -B /path/to/binary-dir -DBUILD_TESTING=NO These are typically done by writing entries to the CMake cache during the configure step. Some projects offer options to enable/disable tests, components, features, etc. Advanced topics Setting options and cache variables Too often you will have to read the build or its documentation to determine which variables need to be set (via -D, like we did with CMAKE_BUILD_TYPE above) for the project to find its dependencies. The most common source of bad behavior in mature CMake builds is dependency handling. If a project fails to build with the above steps and you have all of its dependencies installed to system locations (and they are well behaved), then you should open an issue with the upstream project. These steps assume that the CMake build you are looking at is well behaved. $ cmake -build /path/to/build-dir -config Release This means the build type is chosen during the build step rather than the configure step, and the commands must be adjusted accordingly: $ cmake -S /path/to/source-dir -B /path/to/build-dir If you're on Windows, then the default generator is Visual Studio, which is a multi-config generator. See this answer for more detail on this.Īfter the configure step, you may build the project by either calling the underlying build tool (in this case, make) or by calling CMake's generic build launcher command ( cmake -build), as I do here. The built-in configs are Debug, Release, RelWithDebInfo, and MinSizeRel. You must always set this variable when working with a single-config generator. ![]() When building with a single-config generator (like Make, which is the default on Unix), you specify the build type by setting the CMAKE_BUILD_TYPE variable in the first command, known as the configure step. ![]() You should never attempt an in-tree build with CMake because of the possibility of name clashes and difficulty involved with cleaning up the generated files. Meanwhile, /path/to/build-dir is a distinct directory (that does not need to exist yet) that CMake will use to store the generated build system and its outputs. Here, /path/to/source-dir is the directory containing the root-level CMakeLists.txt, this is most commonly the root of a source control repository. Putting it together, we have $:Release>.If you're on a Unix-y operating system, like Linux or macOS, then you would run: $ cmake -DCMAKE_BUILD_TYPE=Release -S /path/to/source-dir -B /path/to/build-dir This will evaluate to a 1 if the current config is Debug, and to a 0 otherwise. Notice that the step being added is called "BuildOtherConfig," so this inverted logic makes sense. ![]() If the current configuration's Release, it will evaluate to Debug. So, if the current configuration is Debug, the whole expression will evaluate to Release. The one you have there means roughly this (pseudo-code): if current_configuration = "Debug" In short, it's a piece of text which CMake will evaluate at generate time (when it's done parsing all CMakeLists and is generating the buildsystem) it can evaluate to a different value for each configuration. You can follow the link for a full discussion of what these are and what they can do. ![]()
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