zephyr/cmake/target_toolchain.cmake

# No official documentation exists for the "Generic" value, except their wiki.
#
# https://gitlab.kitware.com/cmake/community/wikis/doc/cmake/CrossCompiling:
#   CMAKE_SYSTEM_NAME : this one is mandatory, it is the name of the target
#   system, i.e. the same as CMAKE_SYSTEM_NAME would have if CMake would run
#   on the target system.  Typical examples are "Linux" and "Windows". This
#   variable is used for constructing the file names of the platform files
#   like Linux.cmake or Windows-gcc.cmake. If your target is an embedded
#   system without OS set CMAKE_SYSTEM_NAME to "Generic".
set(CMAKE_SYSTEM_NAME Generic)

# https://cmake.org/cmake/help/latest/variable/CMAKE_SYSTEM_PROCESSOR.html:
#   The name of the CPU CMake is building for.
#
# https://gitlab.kitware.com/cmake/community/wikis/doc/cmake/CrossCompiling:
#   CMAKE_SYSTEM_PROCESSOR : optional, processor (or hardware) of the
#   target system. This variable is not used very much except for one
#   purpose, it is used to load a
#   CMAKE_SYSTEM_NAME-compiler-CMAKE_SYSTEM_PROCESSOR.cmake file,
#   which can be used to modify settings like compiler flags etc. for
#   the target
set(CMAKE_SYSTEM_PROCESSOR ${ARCH})

# https://cmake.org/cmake/help/latest/variable/CMAKE_SYSTEM_VERSION.html:
#   When the CMAKE_SYSTEM_NAME variable is set explicitly to enable cross
#   compiling then the value of CMAKE_SYSTEM_VERSION must also be set
#   explicitly to specify the target system version.
set(CMAKE_SYSTEM_VERSION ${PROJECT_VERSION})

# We are not building dynamically loadable libraries
set(BUILD_SHARED_LIBS OFF)

if(NOT (COMPILER STREQUAL "host-gcc"))
  include(${TOOLCHAIN_ROOT}/cmake/toolchain/${ZEPHYR_TOOLCHAIN_VARIANT}/target.cmake)
endif()

# The 'generic' compiler and the 'target' compiler might be different,
# so we unset the 'generic' one and thereby force the 'target' to
# re-set it.
unset(CMAKE_C_COMPILER)
unset(CMAKE_C_COMPILER CACHE)

# Configure the toolchain based on what toolchain technology is used
# (gcc, host-gcc etc.)
include(${ZEPHYR_BASE}/cmake/compiler/${COMPILER}/target.cmake OPTIONAL)

# Uniquely identify the toolchain wrt. it's capabilities.
#
# What we are looking for, is a signature definition that is defined
# like this:

# Toolchains with the same signature will always support the same set
# of flags.

# It is not clear how this signature should be constructed. The
# strategy chosen is to md5sum the CC binary.

file(MD5 ${CMAKE_C_COMPILER} CMAKE_C_COMPILER_MD5_SUM)
set(TOOLCHAIN_SIGNATURE ${CMAKE_C_COMPILER_MD5_SUM})