# try_compile

Try building some code.

## Try Compiling Whole Projects

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

Added in version 3.25.

Try building a project. Build success returns `TRUE` and build failure returns `FALSE` in `<compileResultVar>`.

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.

Added in version 3.26: This command records a configure-log try_compile event if the `NO_LOG` option is not specified.

Added in version 3.30: If the `PROPAGATE_TOP_LEVEL_INCLUDES_TO_TRY_COMPILE` global property is set to true, `CMAKE_PROJECT_TOP_LEVEL_INCLUDES` is propagated into the project's build configuration.

This command supports an alternate signature for CMake older than 3.25. The signature above is recommended for clarity.

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

## Try Compiling Source Files

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

Added in version 3.25.

Try building an executable or static library from one or more source files. The binary type is determined by variable `CMAKE_TRY_COMPILE_TARGET_TYPE`. Build success returns boolean `true` and build failure returns boolean `false` in `<compileResultVar>` (cached unless `NO_CACHE` is specified).

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 supports an alternate signature for CMake older than 3.25. The signature above is recommended for clarity.

    try_compile(<compileResultVar> <bindir> <srcfile|SOURCES srcfile...>
                [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.

## Options

The options for the above signatures 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 `COMPILE_DEFINITIONS`, `INCLUDE_DIRECTORIES`, `LINK_DIRECTORIES`, `LINK_LIBRARIES`, and `LINK_OPTIONS` are used. Compiler options can be passed in like `CMAKE_FLAGS -DCOMPILE_DEFINITIONS=-Werror`.

`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.

  Added in version 3.29: Alias targets to imported libraries are also supported.

`LINK_OPTIONS <options>...`

  Added 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.

`LINKER_LANGUAGE <lang>`

  Added in version 3.29.

  Specify the `LINKER_LANGUAGE` target property of the generated project. When using multiple source files with different languages, set this to the language of the source file containing the program entry point, e.g., `main`.

`LOG_DESCRIPTION <text>`

  Added in version 3.26.

  Specify a non-empty text description of the purpose of the check. This is recorded in the `cmake-configure-log(7)` entry.

`NO_CACHE`

  Added in version 3.25.

  `<compileResultVar>` will be stored in a normal variable rather than a cache entry.

  `<compileResultVar>` 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.

`NO_LOG`

  Added in version 3.26.

  Do not record a `cmake-configure-log(7)` entry for this call.

`OUTPUT_VARIABLE <var>`

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

`SOURCE_FROM_CONTENT <name> <content>`

  Added 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>`

  Added 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>`

  Added 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.

`SOURCES_TYPE <type>`

  Added in version 3.28.

  Sources may be classified using the `SOURCES_TYPE` argument. Once specified, all subsequent sources specified will be treated as that type until another `SOURCES_TYPE` is given. Available types are:

  `NORMAL`

    Sources are not added to any `FILE_SET` in the generated project.

  `CXX_MODULE`

    Added in version 3.28.

    Sources are added to a `FILE_SET` of type `CXX_MODULES` in the generated project.

  The default type of sources is `NORMAL`.

`<LANG>_STANDARD <std>`

  Added 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>`

  Added 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>`

  Added 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

Added 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:

- `CMAKE_CUDA_RUNTIME_LIBRARY`

- `CMAKE_ENABLE_EXPORTS`

- `CMAKE_EXE_LINKER_FLAGS`, unless using CMake versions prior to 4.0 without policy `CMP0056` set to `NEW`

- `CMAKE_LINK_SEARCH_START_STATIC`

- `CMAKE_LINK_SEARCH_END_STATIC`

- `CMAKE_MSVC_RUNTIME_LIBRARY`

- `CMAKE_POSITION_INDEPENDENT_CODE`

- `CMAKE_WATCOM_RUNTIME_LIBRARY`

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.

Some policies are set automatically in the generated test project as needed to honor the state of the calling project:

- `CMP0065` (in CMake versions prior to 4.0)

- `CMP0083`

- `CMP0091`

- `CMP0104`

- `CMP0123`

- `CMP0126`

- `CMP0128`

- `CMP0136`

- `CMP0141`

- `CMP0155`

- `CMP0157`

- `CMP0181`

- `CMP0184`

Added in version 4.0: The current setting of `CMP0181` policy is propagated through to the generated test project.

Set variable `CMAKE_TRY_COMPILE_CONFIGURATION` to choose a build configuration:

- For multi-config generators, this selects which configuration to build.

- For single-config generators, this sets `CMAKE_BUILD_TYPE` in the test project.

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

Added 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:

- `CMAKE_C_STANDARD`

- `CMAKE_C_STANDARD_REQUIRED`

- `CMAKE_C_EXTENSIONS`

- `CMAKE_CXX_STANDARD`

- `CMAKE_CXX_STANDARD_REQUIRED`

- `CMAKE_CXX_EXTENSIONS`

- `CMAKE_OBJC_STANDARD`

- `CMAKE_OBJC_STANDARD_REQUIRED`

- `CMAKE_OBJC_EXTENSIONS`

- `CMAKE_OBJCXX_STANDARD`

- `CMAKE_OBJCXX_STANDARD_REQUIRED`

- `CMAKE_OBJCXX_EXTENSIONS`

- `CMAKE_CUDA_STANDARD`

- `CMAKE_CUDA_STANDARD_REQUIRED`

- `CMAKE_CUDA_EXTENSIONS`

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.

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

Added 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.

Added in version 3.30: If the `PROPAGATE_TOP_LEVEL_INCLUDES_TO_TRY_COMPILE` global property is set to true, `CMAKE_PROJECT_TOP_LEVEL_INCLUDES` is propagated into the test project's build configuration when using the whole-project signature.

Added in version 4.0: If `CMP0184` is set to `NEW`, one can use `CMAKE_MSVC_RUNTIME_CHECKS` to specify the enabled MSVC runtime checks.

## See Also

- `try_run()`