#Important cmake variables code

#Important cmake variables code

or have its sources directly be included as a sub-folder in the soure code of another bigger project.configured, built and installed in a standalone fashion.With this last setup (and if done properly!), a project can theoritically be either:

Take a look at the official CMake documentation for more details. It also provides the ability to pass more configuration elements than just libraries and binaries (for example user options for compilation, etc …) For example finding HDF5 in CONFIG mode allows to directly reference the “hdf5” target (and to link against it). This mechanism allows to remain in a pure CMake logic, where the package detection triggers the inclusion of the targets it references. CONFIG (or NO_MODULE) mode - if the package was itself compiled with CMake, it might offer a file called xyz-config.cmake or XyzConfig.cmake (where is the case-sensitive name of the package) exposing the configuration elements for an usage by a dependent project.CMake then looks for a file called FindXXX.cmake, pre-sets some variables (indicating if the package is required, etc … see Implementation details (advanced)) and invokes the code in the macro. MODULE mode - this is the standard mode.Note that if you are calling CMake to reconfigure and regenerate an already configured and generated buildsystem for the purposes of changing cache variables, there are several tools which can make that easier for you as well, including the bundled interactive dialogs, cmake-gui and ccmake.When invoking the FIND_PACKAGE() command in CMake, two modes are possible: gitignore) suited exactly for your personal needs. You can create a user-local CMakeUserPresets.json file (put it in your. Actually, CMake's Preset feature sounds right up your alley. Note that most shells have history functionality, so you can recall past commands you've executed. The advantage is not having to remember and/or copy and paste long directory names every time I call cmake If the variable is a boolean, there's a shorthand command for defining a cache variable: option. I've written about this also in my answer to 'CMakePresets.json vs CMakeSettings.json vs CMakeLists.txt'. ) to conditionally only set the variable hasn't been set yet. Note that for potentially non-cache variables, you can do similar using if(DEFINED. Generally speaking, if the variable is something that you think someone building your project might want to have control over, then you should leave it to the user to use -D, and set a 'default value' in your CMakeLists.txt by using set(. You can specify a type, and also a docstring.īoth cache and non-cache variables can be referenced using the same syntax ( docs and related nuance: policy CMP0126). Non-cache variables are scoped to blocks, functions, and directory scopes ( docs). You can also set the type using the TYPE argument. You can pass CACHE to set the variable as a cache variable. If you set the type to PATH or FILEPATH, the value will be converted to an absolute path. D sets variables as cache variables (see also Mastering CMake chapter, and variables docs), which means that even though they aren't set in the configuration files, they will be remembered. Note: My question does not have a specific context but was inspired by following this pytorch tutorial to setup my first C++ project and use pytorch. This answer provides a use case where the two methods are not the same, but is for some specific variable and library I have no knowledge of so can't relate to: Setting '-D' variables inside CMake This answer talks about scope of variables in cmake, and may contain the answer to my question, but it is too convoluted for me to follow: What's the CMake syntax to set and use variables? My question is what is the functional difference between the two methods, and what are some simple use cases where I might not want to use set instead of the command line -D flag? Related Questions The advantage is not having to remember and/or copy and paste long directory names every time I call cmake -DVARIABLE_NAME=path/to/infinity/and/beyond. Rather than using the command line and the -D flag to set variables, I've been using set() inside the CMakeLists.txt for my simple 'learner' one-directory project.