try_compile

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

Try building some code.

Try Compiling Whole Projects

try_compile(RESULT_VAR <bindir> <srcdir>
            <projectName> [<targetName>] [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 RESULT_VAR.

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.

Try Compiling Source Files

try_compile(RESULT_VAR <bindir> <srcfile|SOURCES srcfile...>
            [CMAKE_FLAGS <flags>...]
            [COMPILE_DEFINITIONS <defs>...]
            [LINK_LIBRARIES <libs>...]
            [OUTPUT_VARIABLE <var>]
            [COPY_FILE <fileName> [COPY_FILE_ERROR <var>]])

Try building an executable from one or more source files. The success or failure of the try_compile, i.e. TRUE or FALSE respectively, is returned in RESULT_VAR.

In this form the user need only supply one or more source files that include a definition for main. CMake will create a CMakeLists.txt file to build the source(s) as an executable that looks something like this:

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

The options are:

CMAKE_FLAGS <flags>...

Specify flags of the form -DVAR:TYPE=VALUE to be passed to the cmake 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 linked executable 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.

OUTPUT_VARIABLE <var>

Store the output from the build process the given variable.

In this version all files in <bindir>/CMakeFiles/CMakeTmp will be cleaned automatically. For debugging, --debug-trycompile can be passed to cmake to avoid this clean. However, multiple sequential try_compile operations reuse this single output directory. If you use --debug-trycompile, you can only debug one try_compile call at a time. The recommended procedure is to protect all try_compile calls in your project by if(NOT DEFINED RESULT_VAR) logic, configure with cmake all the way through once, then delete the cache entry associated with the try_compile call of interest, and then re-run cmake again with --debug-trycompile.

Other Behavior Settings

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

• CMAKE_ENABLE_EXPORTS
• CMAKE_LINK_SEARCH_START_STATIC
• CMAKE_LINK_SEARCH_END_STATIC
• CMAKE_POSITION_INDEPENDENT_CODE

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

The current setting of CMP0065 is set in the generated project.

Set the CMAKE_TRY_COMPILE_CONFIGURATION variable to choose a build configuration.

Set the CMAKE_TRY_COMPILE_TARGET_TYPE variable to specify the type of target used for the source file signature.

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.