CMake variables in SCRIPT role

May 15, 2024

When running CMake standalone scripts like cmake -P script.cmake this is the SCRIPT CMake role. Not all CMake information variables are set in SCRIPT role, in particular, the CMAKE_HOST* and CMAKE_SYSTEM* variables are not set as they are in PROJECT role.

This is a workaround for cmake -P SCRIPT role to get the CMAKE_HOST_* variables. It uses undocumented CMake-internal scripts, but they’ve been present since 2012 and may be unlikely to change.

message(STATUS "CMake ${CMAKE_VERSION}")

get_property(cmake_role GLOBAL PROPERTY CMAKE_ROLE)
if(cmake_role STREQUAL "SCRIPT")
  set(CMAKE_PLATFORM_INFO_DIR ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY})
  # define CMAKE_HOST*, CMAKE_SYSTEM*, etc.
  include(${CMAKE_ROOT}/Modules/CMakeDetermineSystem.cmake)
  # set booleans like CYGWIN
  include(${CMAKE_ROOT}/Modules/CMakeSystemSpecificInitialize.cmake)
endif()

message(STATUS "CMAKE_SYSTEM:                ${CMAKE_SYSTEM}")
message(STATUS "CMAKE_SYSTEM_NAME:           ${CMAKE_SYSTEM_NAME}")
message(STATUS "CMAKE_SYSTEM_VERSION:        ${CMAKE_SYSTEM_VERSION}")
message(STATUS "CMAKE_SYSTEM_PROCESSOR:      ${CMAKE_SYSTEM_PROCESSOR}")
message(STATUS "CMAKE_HOST_SYSTEM:           ${CMAKE_HOST_SYSTEM}")
message(STATUS "CMAKE_HOST_SYSTEM_NAME:      ${CMAKE_HOST_SYSTEM_NAME}")
message(STATUS "CMAKE_HOST_SYSTEM_VERSION:   ${CMAKE_HOST_SYSTEM_VERSION}")
message(STATUS "CMAKE_HOST_SYSTEM_PROCESSOR: ${CMAKE_HOST_SYSTEM_PROCESSOR}")