CMAKE-TOOLCHAINS(7) CMake CMAKE-TOOLCHAINS(7)NAMEcmake-toolchains - CMake Toolchains Reference
INTRODUCTION
CMake uses a toolchain of utilities to compile, link libraries and cre‐
ate archives, and other tasks to drive the build. The toolchain utili‐
ties available are determined by the languages enabled. In normal
builds, CMake automatically determines the toolchain for host builds
based on system introspection and defaults. In cross-compiling scenar‐
ios, a toolchain file may be specified with information about compiler
and utility paths.
LANGUAGES
Languages are enabled by the project() command. Language-specific
built-in variables, such as CMAKE_CXX_COMPILER, CMAKE_CXX_COMPILER_ID
etc are set by invoking the project() command. If no project command
is in the top-level CMakeLists file, one will be implicitly generated.
By default the enabled languages are C and CXX:
project(C_Only C)
A special value of NONE can also be used with the project() command to
enable no languages:
project(MyProject NONE)
The enable_language() command can be used to enable languages after the
project() command:
enable_language(CXX)
When a language is enabled, CMake finds a compiler for that language,
and determines some information, such as the vendor and version of the
compiler, the target architecture and bitwidth, the location of corre‐
sponding utilities etc.
The ENABLED_LANGUAGES global property contains the languages which are
currently enabled.
VARIABLES AND PROPERTIES
Several variables relate to the language components of a toolchain
which are enabled. CMAKE_<LANG>_COMPILER is the full path to the com‐
piler used for <LANG>. CMAKE_<LANG>_COMPILER_ID is the identifier used
by CMake for the compiler and CMAKE_<LANG>_COMPILER_VERSION is the ver‐
sion of the compiler.
The CMAKE_<LANG>_FLAGS variables and the configuration-specific equiva‐
lents contain flags that will be added to the compile command when com‐
piling a file of a particular language.
As the linker is invoked by the compiler driver, CMake needs a way to
determine which compiler to use to invoke the linker. This is calcu‐
lated by the LANGUAGE of source files in the target, and in the case of
static libraries, the language of the dependent libraries. The choice
CMake makes may be overridden with the LINKER_LANGUAGE target property.
TOOLCHAIN FEATURES
CMake provides the try_compile() command and wrapper macros such as
CheckCXXSourceCompiles, CheckCXXSymbolExists and CheckIncludeFile to
test capability and availability of various toolchain features. These
APIs test the toolchain in some way and cache the result so that the
test does not have to be performed again the next time CMake runs.
Some toolchain features have built-in handling in CMake, and do not
require compile-tests. For example, POSITION_INDEPENDENT_CODE allows
specifying that a target should be built as position-independent code,
if the compiler supports that feature. The <LANG>_VISIBILITY_PRESET and
VISIBILITY_INLINES_HIDDEN target properties add flags for hidden visi‐
bility, if supported by the compiler.
CROSS COMPILING
If cmake(1) is invoked with the command line parameter
-DCMAKE_TOOLCHAIN_FILE=path/to/file, the file will be loaded early to
set values for the compilers. The CMAKE_CROSSCOMPILING variable is set
to true when CMake is cross-compiling.
Cross Compiling for Linux
A typical cross-compiling toolchain for Linux has content such as:
set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_PROCESSOR arm)
set(CMAKE_SYSROOT /home/devel/rasp-pi-rootfs)
set(CMAKE_STAGING_PREFIX /home/devel/stage)
set(tools /home/devel/gcc-4.7-linaro-rpi-gnueabihf)
set(CMAKE_C_COMPILER ${tools}/bin/arm-linux-gnueabihf-gcc)
set(CMAKE_CXX_COMPILER ${tools}/bin/arm-linux-gnueabihf-g++)
set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)
The CMAKE_SYSTEM_NAME is the CMake-identifier of the target platform to
build for.
The CMAKE_SYSTEM_PROCESSOR is the CMake-identifier of the target archi‐
tecture to build for.
The CMAKE_SYSROOT is optional, and may be specified if a sysroot is
available.
The CMAKE_STAGING_PREFIX is also optional. It may be used to specify a
path on the host to install to. The CMAKE_INSTALL_PREFIX is always the
runtime installation location, even when cross-compiling.
The CMAKE_<LANG>_COMPILER variables may be set to full paths, or to
names of compilers to search for in standard locations. In cases where
CMake does not have enough information to extract information from the
compiler, the CMakeForceCompiler module can be used to bypass some of
the checks.
CMake find_* commands will look in the sysroot, and the
CMAKE_FIND_ROOT_PATH entries by default in all cases, as well as look‐
ing in the host system root prefix. Although this can be controlled on
a case-by-case basis, when cross-compiling, it can be useful to exclude
looking in either the host or the target for particular artifacts. Gen‐
erally, includes, libraries and packages should be found in the target
system prefixes, whereas executables which must be run as part of the
build should be found only on the host and not on the target. This is
the purpose of the CMAKE_FIND_ROOT_PATH_MODE_* variables.
Cross Compiling using Clang
Some compilers such as Clang are inherently cross compilers. The
CMAKE_<LANG>_COMPILER_TARGET can be set to pass a value to those sup‐
ported compilers when compiling:
set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_PROCESSOR arm)
set(triple arm-linux-gnueabihf)
set(CMAKE_C_COMPILER clang)
set(CMAKE_C_COMPILER_TARGET ${triple})
set(CMAKE_CXX_COMPILER clang++)
set(CMAKE_CXX_COMPILER_TARGET ${triple})
Similarly, some compilers do not ship their own supplementary utilities
such as linkers, but provide a way to specify the location of the
external toolchain which will be used by the compiler driver. The
CMAKE_<LANG>_COMPILER_EXTERNAL_TOOLCHAIN variable can be set in a
toolchain file to pass the path to the compiler driver.
Cross Compiling for QNX
As the Clang compiler the QNX QCC compile is inherently a cross com‐
piler. And the CMAKE_<LANG>_COMPILER_TARGET can be set to pass a value
to those supported compilers when compiling:
set(CMAKE_SYSTEM_NAME QNX)
set(arch gcc_ntoarmv7le)
set(CMAKE_C_COMPILER qcc)
set(CMAKE_C_COMPILER_TARGET ${arch})
set(CMAKE_CXX_COMPILER QCC)
set(CMAKE_CXX_COMPILER_TARGET ${arch})
Cross Compiling for Windows CE
Cross compiling for Windows CE requires the corresponding SDK being
installed on your system. These SDKs are usually installed under
C:/Program Files (x86)/Windows CE Tools/SDKs.
A toolchain file to configure a Visual Studio generator for Windows CE
may look like this:
set(CMAKE_SYSTEM_NAME WindowsCE)
set(CMAKE_SYSTEM_VERSION 8.0)
set(CMAKE_SYSTEM_PROCESSOR arm)
set(CMAKE_GENERATOR_TOOLSET CE800) # Can be omitted for 8.0
set(CMAKE_GENERATOR_PLATFORM SDK_AM335X_SK_WEC2013_V310)
The CMAKE_GENERATOR_PLATFORM tells the generator which SDK to use.
Further CMAKE_SYSTEM_VERSION tells the generator what version of Win‐
dows CE to use. Currently version 8.0 (Windows Embedded Compact 2013)
is supported out of the box. Other versions may require one to set
CMAKE_GENERATOR_TOOLSET to the correct value.
Cross Compiling for Windows 10 Universal Applications
A toolchain file to configure a Visual Studio generator for a Windows
10 Universal Application may look like this:
set(CMAKE_SYSTEM_NAME WindowsStore)
set(CMAKE_SYSTEM_VERSION 10.0)
A Windows 10 Universal Application targets both Windows Store and Win‐
dows Phone. Specify the CMAKE_SYSTEM_VERSION variable to be 10.0 to
build with the latest available Windows 10 SDK. Specify a more spe‐
cific version (e.g. 10.0.10240.0 for RTM) to build with the correspond‐
ing SDK.
Cross Compiling for Windows Phone
A toolchain file to configure a Visual Studio generator for Windows
Phone may look like this:
set(CMAKE_SYSTEM_NAME WindowsPhone)
set(CMAKE_SYSTEM_VERSION 8.1)
Cross Compiling for Windows Store
A toolchain file to configure a Visual Studio generator for Windows
Store may look like this:
set(CMAKE_SYSTEM_NAME WindowsStore)
set(CMAKE_SYSTEM_VERSION 8.1)
Cross Compiling using NVIDIA Nsight Tegra
A toolchain file to configure a Visual Studio generator to build using
NVIDIA Nsight Tegra targeting Android may look like this:
set(CMAKE_SYSTEM_NAME Android)
The CMAKE_GENERATOR_TOOLSET may be set to select the Nsight Tegra
"Toolchain Version" value.
See also target properties:
· ANDROID_ANT_ADDITIONAL_OPTIONS
· ANDROID_API_MIN
· ANDROID_API
· ANDROID_ARCH
· ANDROID_ASSETS_DIRECTORIES
· ANDROID_GUI
· ANDROID_JAR_DEPENDENCIES
· ANDROID_JAR_DIRECTORIES
· ANDROID_JAVA_SOURCE_DIR
· ANDROID_NATIVE_LIB_DEPENDENCIES
· ANDROID_NATIVE_LIB_DIRECTORIES
· ANDROID_PROCESS_MAX
· ANDROID_PROGUARD_CONFIG_PATH
· ANDROID_PROGUARD
· ANDROID_SECURE_PROPS_PATH
· ANDROID_SKIP_ANT_STEP
· ANDROID_STL_TYPE
COPYRIGHT
2000-2015 Kitware, Inc.
3.4.2 February 17, 2016 CMAKE-TOOLCHAINS(7)
