1CMAKE_SYSTEM_VERSION
2--------------------
3
4The version of the operating system for which CMake is to build.
5See the :variable:`CMAKE_SYSTEM_NAME` variable for the OS name.
6
7System Version for Host Builds
8^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
9
10When the :variable:`CMAKE_SYSTEM_NAME` variable takes its default value
11then ``CMAKE_SYSTEM_VERSION`` is by default set to the same value as the
12:variable:`CMAKE_HOST_SYSTEM_VERSION` variable so that the build targets
13the host system version.
14
15In the case of a host build then ``CMAKE_SYSTEM_VERSION`` may be set
16explicitly when first configuring a new build tree in order to enable
17targeting the build for a different version of the host operating system
18than is actually running on the host.  This is allowed and not considered
19cross compiling so long as the binaries built for the specified OS version
20can still run on the host.
21
22System Version for Cross Compiling
23^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
24
25When the :variable:`CMAKE_SYSTEM_NAME` variable is set explicitly to
26enable :ref:`cross compiling <Cross Compiling Toolchain>` then the
27value of ``CMAKE_SYSTEM_VERSION`` must also be set explicitly to specify
28the target system version.
29