try_compile

• Try Compiling Whole Projects
• Try Compiling Source Files
• Other Behavior Settings

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>])

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.

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>]
            )

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

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.