try_compile

Try building some code.

Try Compiling Whole Projects

try_compile(<resultVar> PROJECT <projectName>
            SOURCE_DIR <srcdir>
            [BINARY_DIR <bindir>]
            [TARGET <targetName>]
            [NO_CACHE]
            [CMAKE_FLAGS <flags>...]
            [OUTPUT_VARIABLE <var>])

New in version 3.25.

Try building a project. The success or failure of the try_compile, i.e. TRUE or FALSE respectively, is returned in <resultVar>.

In this form, <srcdir> should contain a complete CMake project with a CMakeLists.txt file and all sources. The <bindir> and <srcdir> will not be deleted after this command is run. Specify <targetName> to build a specific target instead of the all or ALL_BUILD target. See below for the meaning of other options.

Changed in version 3.24: CMake variables describing platform settings, and those listed by the CMAKE_TRY_COMPILE_PLATFORM_VARIABLES variable, are propagated into the project's build configuration. See policy CMP0137. Previously this was only done by the source file signature.

This command also supports an alternate signature which was present in older versions of CMake:

try_compile(<resultVar> <bindir> <srcdir>
            <projectName> [<targetName>]
            [NO_CACHE]
            [CMAKE_FLAGS <flags>...]
            [OUTPUT_VARIABLE <var>])

Try Compiling Source Files

try_compile(<resultVar>
            <SOURCES <srcfile...>                 |
             SOURCE_FROM_CONTENT <name> <content> |
             SOURCE_FROM_VAR <name> <var>         |
             SOURCE_FROM_FILE <name> <path>       >...
            [NO_CACHE]
            [CMAKE_FLAGS <flags>...]
            [COMPILE_DEFINITIONS <defs>...]
            [LINK_OPTIONS <options>...]
            [LINK_LIBRARIES <libs>...]
            [OUTPUT_VARIABLE <var>]
            [COPY_FILE <fileName> [COPY_FILE_ERROR <var>]]
            [<LANG>_STANDARD <std>]
            [<LANG>_STANDARD_REQUIRED <bool>]
            [<LANG>_EXTENSIONS <bool>]
            )

New in version 3.25.

Try building an executable or static library from one or more source files (which one is determined by the CMAKE_TRY_COMPILE_TARGET_TYPE variable). The success or failure of the try_compile, i.e. TRUE or FALSE respectively, is returned in <resultVar>.

In this form, one or more source files must be provided. Additionally, one of SOURCES and/or SOURCE_FROM_* must precede other keywords.

If CMAKE_TRY_COMPILE_TARGET_TYPE is unset or is set to EXECUTABLE, the sources must include a definition for main and CMake will create a CMakeLists.txt file to build the source(s) as an executable. If CMAKE_TRY_COMPILE_TARGET_TYPE is set to STATIC_LIBRARY, a static library will be built instead and no definition for main is required. For an executable, the generated CMakeLists.txt file would contain something like the following:

add_definitions(<expanded COMPILE_DEFINITIONS from caller>)
include_directories(${INCLUDE_DIRECTORIES})
link_directories(${LINK_DIRECTORIES})
add_executable(cmTryCompileExec <srcfile>...)
target_link_options(cmTryCompileExec PRIVATE <LINK_OPTIONS from caller>)
target_link_libraries(cmTryCompileExec ${LINK_LIBRARIES})

CMake automatically generates, for each try_compile operation, a unique directory under ${CMAKE_BINARY_DIR}/CMakeFiles/CMakeScratch with an unspecified name. These directories are cleaned automatically unless --debug-trycompile is passed to cmake. Such directories from previous runs are also unconditionally cleaned at the beginning of any cmake execution.

This command also supports an alternate signature which was present in older versions of CMake:

try_compile(<resultVar> <bindir> <srcfile|SOURCES srcfile...>
            [NO_CACHE]
            [CMAKE_FLAGS <flags>...]
            [COMPILE_DEFINITIONS <defs>...]
            [LINK_OPTIONS <options>...]
            [LINK_LIBRARIES <libs>...]
            [OUTPUT_VARIABLE <var>]
            [COPY_FILE <fileName> [COPY_FILE_ERROR <var>]]
            [<LANG>_STANDARD <std>]
            [<LANG>_STANDARD_REQUIRED <bool>]
            [<LANG>_EXTENSIONS <bool>]
            )

In this version, try_compile will use <bindir>/CMakeFiles/CMakeTmp for its operation, and all such files will be cleaned automatically. For debugging, --debug-trycompile can be passed to cmake to avoid this clean. However, multiple sequential try_compile operations, if given the same <bindir>, will reuse this single output directory, such that you can only debug one such try_compile call at a time. Use of the newer signature is recommended to simplify debugging of multiple try_compile operations.

The options are:

CMAKE_FLAGS <flags>...

Specify flags of the form -DVAR:TYPE=VALUE to be passed to the cmake(1) command-line used to drive the test build. The above example shows how values for variables INCLUDE_DIRECTORIES, LINK_DIRECTORIES, and LINK_LIBRARIES are used.

COMPILE_DEFINITIONS <defs>...

Specify -Ddefinition arguments to pass to add_definitions() in the generated test project.

COPY_FILE <fileName>

Copy the built executable or static library to the given <fileName>.

COPY_FILE_ERROR <var>

Use after COPY_FILE to capture into variable <var> any error message encountered while trying to copy the file.

LINK_LIBRARIES <libs>...

Specify libraries to be linked in the generated project. The list of libraries may refer to system libraries and to Imported Targets from the calling project.

If this option is specified, any -DLINK_LIBRARIES=... value given to the CMAKE_FLAGS option will be ignored.

LINK_OPTIONS <options>...

New in version 3.14.

Specify link step options to pass to target_link_options() or to set the STATIC_LIBRARY_OPTIONS target property in the generated project, depending on the CMAKE_TRY_COMPILE_TARGET_TYPE variable.

NO_CACHE

New in version 3.25.

The result will be stored in a normal variable rather than a cache entry.

The result variable is normally cached so that a simple pattern can be used to avoid repeating the test on subsequent executions of CMake:

if(NOT DEFINED RESULTVAR)
  # ...(check-specific setup code)...
  try_compile(RESULTVAR ...)
  # ...(check-specific logging and cleanup code)...
endif()

If the guard variable and result variable are not the same (for example, if the test is part of a larger inspection), NO_CACHE may be useful to avoid leaking the intermediate result variable into the cache.

OUTPUT_VARIABLE <var>

Store the output from the build process in the given variable.

SOURCE_FROM_CONTENT <name> <content>

New in version 3.25.

Write <content> to a file named <name> in the operation directory. This can be used to bypass the need to separately write a source file when the contents of the file are dynamically specified. The specified <name> is not allowed to contain path components.

SOURCE_FROM_CONTENT may be specified multiple times.

SOURCE_FROM_FILE <name> <path>

New in version 3.25.

Copy <path> to a file named <name> in the operation directory. This can be used to consolidate files into the operation directory, which may be useful if a source which already exists (i.e. as a stand-alone file in a project's source repository) needs to refer to other file(s) created by SOURCE_FROM_*. (Otherwise, SOURCES is usually more convenient.) The specified <name> is not allowed to contain path components.

SOURCE_FROM_VAR <name> <var>

New in version 3.25.

Write the contents of <var> to a file named <name> in the operation directory. This is the same as SOURCE_FROM_CONTENT, but takes the contents from the specified CMake variable, rather than directly, which may be useful when passing arguments through a function which wraps try_compile. The specified <name> is not allowed to contain path components.

SOURCE_FROM_VAR may be specified multiple times.

<LANG>_STANDARD <std>

New in version 3.8.

Specify the C_STANDARD, CXX_STANDARD, OBJC_STANDARD, OBJCXX_STANDARD, or CUDA_STANDARD target property of the generated project.

<LANG>_STANDARD_REQUIRED <bool>

New in version 3.8.

Specify the C_STANDARD_REQUIRED, CXX_STANDARD_REQUIRED, OBJC_STANDARD_REQUIRED, OBJCXX_STANDARD_REQUIRED,or CUDA_STANDARD_REQUIRED target property of the generated project.

<LANG>_EXTENSIONS <bool>

New in version 3.8.

Specify the C_EXTENSIONS, CXX_EXTENSIONS, OBJC_EXTENSIONS, OBJCXX_EXTENSIONS, or CUDA_EXTENSIONS target property of the generated project.

Other Behavior Settings

New in version 3.4: If set, the following variables are passed in to the generated try_compile CMakeLists.txt to initialize compile target properties with default values:

If CMP0056 is set to NEW, then CMAKE_EXE_LINKER_FLAGS is passed in as well.

Changed in version 3.14: If CMP0083 is set to NEW, then in order to obtain correct behavior at link time, the check_pie_supported() command from the CheckPIESupported module must be called before using the try_compile() command.

The current settings of CMP0065 and CMP0083 are propagated through to the generated test project.

Set the CMAKE_TRY_COMPILE_CONFIGURATION variable to choose a build configuration.

New in version 3.6: Set the CMAKE_TRY_COMPILE_TARGET_TYPE variable to specify the type of target used for the source file signature.

New in version 3.6: Set the CMAKE_TRY_COMPILE_PLATFORM_VARIABLES variable to specify variables that must be propagated into the test project. This variable is meant for use only in toolchain files and is only honored by the try_compile() command for the source files form, not when given a whole project.

Changed in version 3.8: If CMP0067 is set to NEW, or any of the <LANG>_STANDARD, <LANG>_STANDARD_REQUIRED, or <LANG>_EXTENSIONS options are used, then the language standard variables are honored:

Their values are used to set the corresponding target properties in the generated project (unless overridden by an explicit option).

Changed in version 3.14: For the Green Hills MULTI generator, the GHS toolset and target system customization cache variables are also propagated into the test project.

New in version 3.24: The CMAKE_TRY_COMPILE_NO_PLATFORM_VARIABLES variable may be set to disable passing platform variables into the test project.

New in version 3.25: If CMP0141 is set to NEW, one can use CMAKE_MSVC_DEBUG_INFORMATION_FORMAT to specify the MSVC debug information format.