System install on UNIX would often be /usr/local (the default), user directories are often ~/.local, or you can pick a folder. -DCMAKE_INSTALL_PREFIX= The location to install to.-DCMAKE_BUILD_TYPE= Pick from Release, RelWithDebInfo, Debug, or sometimes more.These are common CMake options to most packages: When CMake looks for a cached variable, it will use the existing value and will not overwrite it. You can preset (or change) the value of a cached option on the command line with -D. A Variable in CMake can be marked as "cached", which means it will be written to the cache (a file called CMakeCache.txt in the build directory) when it is encountered. OptionsĬMake has support for cached options. You can also build just a part of a build by specifying a target, such as the name of a library or executable you've defined in CMake, and make will just build that target. You can actually write make VERBOSE=1, and make will also do the right thing, though that's a feature of make and not the command line in general. ~/package $ cmake -build build -verbose # CMake 3.14+ only ~/package/build $ VERBOSE=1 make Verbose and partial buildsĪlthough not all build tools support it, you can get verbose builds (pick one): If you don't list the source/build directory, the listing will not rerun CMake ( cmake -L instead of cmake -L. You can see a list of options with -L, or a list with human-readable help with -LH. You can directly pass a parallelization option such as -j2 to the cmake -build. Note that makefiles will only run in parallel if you explicitly pass a number of threads, such as make -j2, while Ninja will automatically run in parallel. You can set the environment variable CMAKE_GENERATOR to control the default generator (CMake 3.15+). Feel free to have several build directories, like build/ and buildXcode. You should pick a tool on your first CMake call in a directory, just like the compiler. To see all the tools CMake knows about on your system, runĪnd you can pick a tool with -G"My Tool" (quotes only needed if spaces are in the tool name). You can build with a variety of tools make is usually the default. This sets it just for that one line, but that's the only time you'll need those afterwards CMake continues to use the paths it deduces from those values. That sets the environment variables in bash for CC and CXX, and CMake will respect those variables. ~/package/build $ CC=clang CXX=clang++ cmake. It's not CMake syntax per se, but you might not be familiar with it. Selecting a compiler must be done on the first run in an empty directory. You can instead use the environment variables for these, as well, such as CMAKE_BUILD_PARALLEL_LEVEL (CMake 3.12+) and VERBOSE (CMake 3.14+). Otherwise, these commands vary between build systems, such as VERBOSE=1 make and ninja -v. If you use cmake -build instead of directly calling the underlying build system, you can use -v for verbose builds (CMake 3.14+), -j N for parallel builds on N cores (CMake 3.12+), and -target (any version of CMake) or -t (CMake 3.15+) to pick a target. Just to clarify, you can point CMake at either the source directory from the build directory, or at an existing build directory from anywhere. Note that working from the build directory is historically much more common, and some tools and commands (including CTest <3.20) still require running from the build directory. You should try to get used to using -build, as that will free you from using only make to build. So which set of methods should you use? As long as you do not forget to type the build directory as the argument, staying out of the build directory is shorter, and making source changes is easier from the source directory. # CMake 3.15+ only # From the source directory (pick one) ~/package $ make -C build install ~/package $ cmake -build build -target install ~/package $ cmake -install build # CMake 3.15+ only target install ~/package/build $ cmake -install. # From the build directory (pick one) ~/package/build $ make install ~/package/build $ cmake -build. If you are using a newer version of CMake (which you usually should be, except for checking compatibility with older CMake), you can instead do this: if you'd like, and it will call make or whatever build tool you are using. You can replace the make line with cmake -build. ~/package $ mkdir build ~/package $ cd build ~/package/build $ cmake. Here's the Classic CMake Build Procedure (TM): You can technically do an in-source build, but you'll have to be careful not to overwrite files or add them to git, so just don't. Unless otherwise noted, you should always make a build directory and build from there. This is true for almost all CMake projects, which is almost everything. Before writing CMake, let's make sure you know how to run it to make things.
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