Variables customize how the build will be generated. Options are boolean variables, with possible values ON/OFF. Options and variables are defined on the CMake command line like this:
$ cmake -DVARIABLE=value path/to/hpx
You can set a variable after the initial CMake invocation for changing its value. You can also undefine a variable:
$ cmake -UVARIABLE path/to/hpx
Variables are stored on the CMake cache. This is a file named CMakeCache.txt on the root of the build directory. Do not hand-edit it.
Variables are listed here appending its type after a colon. It is correct to write the variable and the type on the CMake command line:
$ cmake -DVARIABLE:TYPE=value path/to/llvm/source
CMake supports the following variable types:
STRING (arbitrary string),
PATH (directory name),
FILEPATH (file name).