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CMAKE-TOOLCHAINS(7) CMake CMAKE-TOOLCHAINS(7)

NAME
cmake-toolchains - CMake Toolchains Reference

INTRODUCTION
CMake uses a toolchain of utilities to compile, link libraries and
create archives, and other tasks to drive the build. The toolchain
utilities 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
scenarios, a toolchain file may be specified with information about
compiler and utility paths.

New in version 3.19: One may use cmake-presets(7) to specify toolchain
files.

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
corresponding 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
The full path to the compiler used for <LANG>

CMAKE_<LANG>_COMPILER_ID
The compiler identifier used by CMake

CMAKE_<LANG>_COMPILER_VERSION
The version of the compiler.

CMAKE_<LANG>_FLAGS
The variables and the configuration-specific equivalents contain
flags that will be added to the compile command when compiling a
file of a particular language.

CMake needs a way to determine which compiler to use to invoke the
linker. This is determined by the LANGUAGE property of source files of
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
visibility, if supported by the compiler.

CROSS COMPILING
If cmake(1) is invoked with the command line parameter --toolchain
path/to/file or -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.

Note that using the CMAKE_SOURCE_DIR or CMAKE_BINARY_DIR variables
inside a toolchain file is typically undesirable. The toolchain file
is used in contexts where these variables have different values when
used in different places (e.g. as part of a call to try_compile()). In
most cases, where there is a need to evaluate paths inside a toolchain
file, the more appropriate variable to use would be
CMAKE_CURRENT_LIST_DIR, since it always has an unambiguous, predictable
value.

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)

Where:

CMAKE_SYSTEM_NAME
is the CMake-identifier of the target platform to build for.

CMAKE_SYSTEM_PROCESSOR
is the CMake-identifier of the target architecture.

CMAKE_SYSROOT
is optional, and may be specified if a sysroot is available.

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.

CMAKE_<LANG>_COMPILER
variable may be set to full paths, or to names of compilers to
search for in standard locations. For toolchains that do not
support linking binaries without custom flags or scripts one may
set the CMAKE_TRY_COMPILE_TARGET_TYPE variable to STATIC_LIBRARY
to tell CMake not to try to link executables during its checks.

CMake find_* commands will look in the sysroot, and the
CMAKE_FIND_ROOT_PATH entries by default in all cases, as well as
looking 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. Generally, 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 for the Cray Linux Environment
Cross compiling for compute nodes in the Cray Linux Environment can be
done without needing a separate toolchain file. Specifying
-DCMAKE_SYSTEM_NAME=CrayLinuxEnvironment on the CMake command line will
ensure that the appropriate build settings and search paths are
configured. The platform will pull its configuration from the current
environment variables and will configure a project to use the compiler
wrappers from the Cray Programming Environment's PrgEnv-* modules if
present and loaded.

The default configuration of the Cray Programming Environment is to
only support static libraries. This can be overridden and shared
libraries enabled by setting the CRAYPE_LINK_TYPE environment variable
to dynamic.

Running CMake without specifying CMAKE_SYSTEM_NAME will run the
configure step in host mode assuming a standard Linux environment. If
not overridden, the PrgEnv-* compiler wrappers will end up getting
used, which if targeting the either the login node or compute node, is
likely not the desired behavior. The exception to this would be if you
are building directly on a NID instead of cross-compiling from a login
node. If trying to build software for a login node, you will need to
either first unload the currently loaded PrgEnv-* module or explicitly
tell CMake to use the system compilers in /usr/bin instead of the Cray
wrappers. If instead targeting a compute node is desired, just specify
the CMAKE_SYSTEM_NAME as mentioned above.

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
supported 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
compiler. 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})

set(CMAKE_SYSROOT $ENV{QNX_TARGET})

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
Windows 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
Windows Phone. Specify the CMAKE_SYSTEM_VERSION variable to be 10.0 to
build with the latest available Windows 10 SDK. Specify a more
specific version (e.g. 10.0.10240.0 for RTM) to build with the
corresponding 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 for ADSP SHARC/Blackfin
Cross-compiling for ADSP SHARC or Blackfin can be configured by setting
the CMAKE_SYSTEM_NAME variable to ADSP and the CMAKE_SYSTEM_PROCESSOR
variable to the "part number", excluding the ADSP- prefix, for example,
21594, SC589, etc. This value is case insensitive.

CMake will automatically search for CCES or VDSP++ installs in their
default install locations and select the most recent version found.
CCES will be selected over VDSP++ if both are installed. Custom
install paths can be set via the CMAKE_ADSP_ROOT variable or the
ADSP_ROOT environment variable.

The compiler (cc21k vs. ccblkfn) is selected automatically based on the
CMAKE_SYSTEM_PROCESSOR value provided.

Cross Compiling for Android
A toolchain file may configure cross-compiling for Android by setting
the CMAKE_SYSTEM_NAME variable to Android. Further configuration is
specific to the Android development environment to be used.

For Visual Studio Generators, CMake expects NVIDIA Nsight Tegra Visual
Studio Edition or the Visual Studio tools for Android to be installed.
See those sections for further configuration details.

For Makefile Generators and the Ninja generator, CMake expects one of
these environments:

o NDK

o Standalone Toolchain

CMake uses the following steps to select one of the environments:

o If the CMAKE_ANDROID_NDK variable is set, the NDK at the specified
location will be used.

o Else, if the CMAKE_ANDROID_STANDALONE_TOOLCHAIN variable is set, the
Standalone Toolchain at the specified location will be used.

o Else, if the CMAKE_SYSROOT variable is set to a directory of the form
<ndk>/platforms/android-<api>/arch-<arch>, the <ndk> part will be
used as the value of CMAKE_ANDROID_NDK and the NDK will be used.

o Else, if the CMAKE_SYSROOT variable is set to a directory of the form
<standalone-toolchain>/sysroot, the <standalone-toolchain> part will
be used as the value of CMAKE_ANDROID_STANDALONE_TOOLCHAIN and the
Standalone Toolchain will be used.

o Else, if a cmake variable ANDROID_NDK is set it will be used as the
value of CMAKE_ANDROID_NDK, and the NDK will be used.

o Else, if a cmake variable ANDROID_STANDALONE_TOOLCHAIN is set, it
will be used as the value of CMAKE_ANDROID_STANDALONE_TOOLCHAIN, and
the Standalone Toolchain will be used.

o Else, if an environment variable ANDROID_NDK_ROOT or ANDROID_NDK is
set, it will be used as the value of CMAKE_ANDROID_NDK, and the NDK
will be used.

o Else, if an environment variable ANDROID_STANDALONE_TOOLCHAIN is set
then it will be used as the value of
CMAKE_ANDROID_STANDALONE_TOOLCHAIN, and the Standalone Toolchain will
be used.

o Else, an error diagnostic will be issued that neither the NDK or
Standalone Toolchain can be found.

New in version 3.20: If an Android NDK is selected, its version number
is reported in the CMAKE_ANDROID_NDK_VERSION variable.

Cross Compiling for Android with the NDK
A toolchain file may configure Makefile Generators, Ninja Generators,
or Visual Studio Generators to target Android for cross-compiling.

Configure use of an Android NDK with the following variables:

CMAKE_SYSTEM_NAME
Set to Android. Must be specified to enable cross compiling for
Android.

CMAKE_SYSTEM_VERSION
Set to the Android API level. If not specified, the value is
determined as follows:

o If the CMAKE_ANDROID_API variable is set, its value is used as
the API level.

o If the CMAKE_SYSROOT variable is set, the API level is
detected from the NDK directory structure containing the
sysroot.

o Otherwise, the latest API level available in the NDK is used.

CMAKE_ANDROID_ARCH_ABI
Set to the Android ABI (architecture). If not specified, this
variable will default to the first supported ABI in the list of
armeabi, armeabi-v7a and arm64-v8a. The CMAKE_ANDROID_ARCH
variable will be computed from CMAKE_ANDROID_ARCH_ABI
automatically. Also see the CMAKE_ANDROID_ARM_MODE and
CMAKE_ANDROID_ARM_NEON variables.

CMAKE_ANDROID_NDK
Set to the absolute path to the Android NDK root directory. If
not specified, a default for this variable will be chosen as
specified above.

CMAKE_ANDROID_NDK_DEPRECATED_HEADERS
Set to a true value to use the deprecated per-api-level headers
instead of the unified headers. If not specified, the default
will be false unless using a NDK that does not provide unified
headers.

CMAKE_ANDROID_NDK_TOOLCHAIN_VERSION
On NDK r19 or above, this variable must be unset or set to
clang. On NDK r18 or below, set this to the version of the NDK
toolchain to be selected as the compiler. If not specified, the
default will be the latest available GCC toolchain.

CMAKE_ANDROID_STL_TYPE
Set to specify which C++ standard library to use. If not
specified, a default will be selected as described in the
variable documentation.

The following variables will be computed and provided automatically:

CMAKE_<LANG>_ANDROID_TOOLCHAIN_PREFIX
The absolute path prefix to the binutils in the NDK toolchain.

CMAKE_<LANG>_ANDROID_TOOLCHAIN_SUFFIX
The host platform suffix of the binutils in the NDK toolchain.

For example, a toolchain file might contain:

set(CMAKE_SYSTEM_NAME Android)
set(CMAKE_SYSTEM_VERSION 21) # API level
set(CMAKE_ANDROID_ARCH_ABI arm64-v8a)
set(CMAKE_ANDROID_NDK /path/to/android-ndk)
set(CMAKE_ANDROID_STL_TYPE gnustl_static)

Alternatively one may specify the values without a toolchain file:

$ cmake ../src \
-DCMAKE_SYSTEM_NAME=Android \
-DCMAKE_SYSTEM_VERSION=21 \
-DCMAKE_ANDROID_ARCH_ABI=arm64-v8a \
-DCMAKE_ANDROID_NDK=/path/to/android-ndk \
-DCMAKE_ANDROID_STL_TYPE=gnustl_static

Cross Compiling for Android with a Standalone Toolchain
A toolchain file may configure Makefile Generators or the Ninja
generator to target Android for cross-compiling using a standalone
toolchain.

Configure use of an Android standalone toolchain with the following
variables:

CMAKE_SYSTEM_NAME
Set to Android. Must be specified to enable cross compiling for
Android.

CMAKE_ANDROID_STANDALONE_TOOLCHAIN
Set to the absolute path to the standalone toolchain root
directory. A ${CMAKE_ANDROID_STANDALONE_TOOLCHAIN}/sysroot
directory must exist. If not specified, a default for this
variable will be chosen as specified above.

CMAKE_ANDROID_ARM_MODE
When the standalone toolchain targets ARM, optionally set this
to ON to target 32-bit ARM instead of 16-bit Thumb. See
variable documentation for details.

CMAKE_ANDROID_ARM_NEON
When the standalone toolchain targets ARM v7, optionally set
thisto ON to target ARM NEON devices. See variable
documentation for details.

The following variables will be computed and provided automatically:

CMAKE_SYSTEM_VERSION
The Android API level detected from the standalone toolchain.

CMAKE_ANDROID_ARCH_ABI
The Android ABI detected from the standalone toolchain.

CMAKE_<LANG>_ANDROID_TOOLCHAIN_PREFIX
The absolute path prefix to the binutils in the standalone
toolchain.

CMAKE_<LANG>_ANDROID_TOOLCHAIN_SUFFIX
The host platform suffix of the binutils in the standalone
toolchain.

For example, a toolchain file might contain:

set(CMAKE_SYSTEM_NAME Android)
set(CMAKE_ANDROID_STANDALONE_TOOLCHAIN /path/to/android-toolchain)

Alternatively one may specify the values without a toolchain file:

$ cmake ../src \
-DCMAKE_SYSTEM_NAME=Android \
-DCMAKE_ANDROID_STANDALONE_TOOLCHAIN=/path/to/android-toolchain

Cross Compiling for Android with NVIDIA Nsight Tegra Visual Studio Edition
A toolchain file to configure one of the Visual Studio Generators 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:

o ANDROID_ANT_ADDITIONAL_OPTIONS

o ANDROID_API_MIN

o ANDROID_API

o ANDROID_ARCH

o ANDROID_ASSETS_DIRECTORIES

o ANDROID_GUI

o ANDROID_JAR_DEPENDENCIES

o ANDROID_JAR_DIRECTORIES

o ANDROID_JAVA_SOURCE_DIR

o ANDROID_NATIVE_LIB_DEPENDENCIES

o ANDROID_NATIVE_LIB_DIRECTORIES

o ANDROID_PROCESS_MAX

o ANDROID_PROGUARD_CONFIG_PATH

o ANDROID_PROGUARD

o ANDROID_SECURE_PROPS_PATH

o ANDROID_SKIP_ANT_STEP

o ANDROID_STL_TYPE

Cross Compiling for iOS, tvOS, or watchOS
For cross-compiling to iOS, tvOS, or watchOS, the Xcode generator is
recommended. The Unix Makefiles or Ninja generators can also be used,
but they require the project to handle more areas like target CPU
selection and code signing.

Any of the three systems can be targeted by setting the
CMAKE_SYSTEM_NAME variable to a value from the table below. By
default, the latest Device SDK is chosen. As for all Apple platforms,
a different SDK (e.g. a simulator) can be selected by setting the
CMAKE_OSX_SYSROOT variable, although this should rarely be necessary
(see Switching Between Device and Simulator below). A list of
available SDKs can be obtained by running xcodebuild -showsdks.

For example, to create a CMake configuration for iOS, the following
command is sufficient:

cmake .. -GXcode -DCMAKE_SYSTEM_NAME=iOS

Variable CMAKE_OSX_ARCHITECTURES can be used to set architectures for
both device and simulator. Variable CMAKE_OSX_DEPLOYMENT_TARGET can be
used to set an iOS/tvOS/watchOS deployment target.

Next configuration will install fat 5 architectures iOS library and add
the -miphoneos-version-min=9.3/-mios-simulator-version-min=9.3 flags to
the compiler:

$ cmake -S. -B_builds -GXcode \
-DCMAKE_SYSTEM_NAME=iOS \
"-DCMAKE_OSX_ARCHITECTURES=armv7;armv7s;arm64;i386;x86_64" \
-DCMAKE_OSX_DEPLOYMENT_TARGET=9.3 \
-DCMAKE_INSTALL_PREFIX=`pwd`/_install \
-DCMAKE_XCODE_ATTRIBUTE_ONLY_ACTIVE_ARCH=NO \
-DCMAKE_IOS_INSTALL_COMBINED=YES

Example:

# CMakeLists.txt
cmake_minimum_required(VERSION 3.14)
project(foo)
add_library(foo foo.cpp)
install(TARGETS foo DESTINATION lib)

Install:

$ cmake --build _builds --config Release --target install

Check library:

$ lipo -info _install/lib/libfoo.a
Architectures in the fat file: _install/lib/libfoo.a are: i386 armv7 armv7s x86_64 arm64

$ otool -l _install/lib/libfoo.a | grep -A2 LC_VERSION_MIN_IPHONEOS
cmd LC_VERSION_MIN_IPHONEOS
cmdsize 16
version 9.3

Code Signing
Some build artifacts for the embedded Apple platforms require mandatory
code signing. If the Xcode generator is being used and code signing is
required or desired, the development team ID can be specified via the
CMAKE_XCODE_ATTRIBUTE_DEVELOPMENT_TEAM CMake variable. This team ID
will then be included in the generated Xcode project. By default,
CMake avoids the need for code signing during the internal
configuration phase (i.e compiler ID and feature detection).

Switching Between Device and Simulator
When configuring for any of the embedded platforms, one can target
either real devices or the simulator. Both have their own separate
SDK, but CMake only supports specifying a single SDK for the
configuration phase. This means the developer must select one or the
other at configuration time. When using the Xcode generator, this is
less of a limitation because Xcode still allows you to build for either
a device or a simulator, even though configuration was only performed
for one of the two. From within the Xcode IDE, builds are performed
for the selected "destination" platform. When building from the
command line, the desired sdk can be specified directly by passing a
-sdk option to the underlying build tool (xcodebuild). For example:

$ cmake --build ... -- -sdk iphonesimulator

Please note that checks made during configuration were performed
against the configure-time SDK and might not hold true for other SDKs.
Commands like find_package(), find_library(), etc. store and use
details only for the configured SDK/platform, so they can be
problematic if wanting to switch between device and simulator builds.
You can follow the next rules to make device + simulator configuration
work:

o Use explicit -l linker flag, e.g. target_link_libraries(foo PUBLIC
"-lz")

o Use explicit -framework linker flag, e.g. target_link_libraries(foo
PUBLIC "-framework CoreFoundation")

o Use find_package() only for libraries installed with
CMAKE_IOS_INSTALL_COMBINED feature

3.26.1 September 28, 2023 CMAKE-TOOLCHAINS(7)

DragonFly On-Line Manual Pages

NAME

INTRODUCTION

LANGUAGES

VARIABLES AND PROPERTIES

TOOLCHAIN FEATURES

CROSS COMPILING

COPYRIGHT