# try_run

Try compiling and then running some code.

## Try Compiling and Running Source Files

    try_run(<runResultVar> <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>...]
            [COMPILE_OUTPUT_VARIABLE <var>]
            [COPY_FILE <fileName> [COPY_FILE_ERROR <var>]]
            [<LANG>_STANDARD <std>]
            [<LANG>_STANDARD_REQUIRED <bool>]
            [<LANG>_EXTENSIONS <bool>]
            [RUN_OUTPUT_VARIABLE <var>]
            [RUN_OUTPUT_STDOUT_VARIABLE <var>]
            [RUN_OUTPUT_STDERR_VARIABLE <var>]
            [WORKING_DIRECTORY <var>]
            [ARGS <args>...]
            )

Added in version 3.25.

Try building an executable from one or more source files. Build success returns boolean `true` and build failure returns boolean `false` in `<compileResultVar>` (cached unless `NO_CACHE` is specified). If the build succeeds, this runs the executable and stores the exit code in `<runResultVar>` (cached unless `NO_CACHE` is specified). If the executable was built, but failed to run, then `<runResultVar>` will be set to `FAILED_TO_RUN`. See command `try_compile()` for documentation of options common to both commands, and for information on how the test project is constructed to build the source file.

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

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

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

    try_run(<runResultVar> <compileResultVar>
            <bindir> {<srcfile>|SOURCES <srcfile>...}
            [CMAKE_FLAGS <flags>...]
            [COMPILE_DEFINITIONS <defs>...]
            [LINK_OPTIONS <options>...]
            [LINK_LIBRARIES <libs>...]
            [LINKER_LANGUAGE <lang>]
            [COMPILE_OUTPUT_VARIABLE <var>]
            [COPY_FILE <fileName> [COPY_FILE_ERROR <var>]]
            [<LANG>_STANDARD <std>]
            [<LANG>_STANDARD_REQUIRED <bool>]
            [<LANG>_EXTENSIONS <bool>]
            [RUN_OUTPUT_VARIABLE <var>]
            [OUTPUT_VARIABLE <var>]
            [WORKING_DIRECTORY <var>]
            [ARGS <args>...]
            )

## Options

The options specific to `try_run` are:

`COMPILE_OUTPUT_VARIABLE <var>`

  Report the compile step build output in a given variable.

`OUTPUT_VARIABLE <var>`

  Report the compile build output and the output from running the executable in the given variable. This option exists for legacy reasons and is only supported by the old `try_run` signature. Prefer `COMPILE_OUTPUT_VARIABLE` and `RUN_OUTPUT_VARIABLE` instead.

`RUN_OUTPUT_VARIABLE <var>`

  Report the output from running the executable in a given variable.

`RUN_OUTPUT_STDOUT_VARIABLE <var>`

  Added in version 3.25.

  Report the output of stdout from running the executable in a given variable.

`RUN_OUTPUT_STDERR_VARIABLE <var>`

  Added in version 3.25.

  Report the output of stderr from running the executable in a given variable.

`WORKING_DIRECTORY <var>`

  Added in version 3.20.

  Run the executable in the given directory. If no `WORKING_DIRECTORY` is specified, the executable will run in `<bindir>` or the current build directory.

`ARGS <args>...`

  Additional arguments to pass to the executable when running it.

## Other Behavior Settings

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.

## Behavior when Cross Compiling

Added in version 3.3: Use `CMAKE_CROSSCOMPILING_EMULATOR` when running cross-compiled binaries.

When cross compiling, the executable compiled in the first step usually cannot be run on the build host. The `try_run` command checks the `CMAKE_CROSSCOMPILING` variable to detect whether CMake is in cross-compiling mode. If that is the case, it will still try to compile the executable, but it will not try to run the executable unless the `CMAKE_CROSSCOMPILING_EMULATOR` variable is set. Instead it will create cache variables which must be filled by the user or by presetting them in some CMake script file to the values the executable would have produced if it had been run on its actual target platform. These cache entries are:

`<runResultVar>`

  Exit code if the executable were to be run on the target platform.

`<runResultVar>__TRYRUN_OUTPUT`

  Output from stdout and stderr if the executable were to be run on the target platform. This is created only if the `RUN_OUTPUT_VARIABLE` or `OUTPUT_VARIABLE` option was used.

`<runResultVar>__TRYRUN_OUTPUT_STDOUT`

  Added in version 3.25.

  Output from stdout if the executable were to be run on the target platform. This is created only if the `RUN_OUTPUT_STDOUT_VARIABLE` or `RUN_OUTPUT_STDERR_VARIABLE` option was used.

`<runResultVar>__TRYRUN_OUTPUT_STDERR`

  Added in version 3.25.

  Output from stderr if the executable were to be run on the target platform. This is created only if the `RUN_OUTPUT_STDOUT_VARIABLE` or `RUN_OUTPUT_STDERR_VARIABLE` option was used.

In order to make cross compiling your project easier, use `try_run` only if really required. If you use `try_run`, use the `RUN_OUTPUT_STDOUT_VARIABLE`, `RUN_OUTPUT_STDERR_VARIABLE`, `RUN_OUTPUT_VARIABLE` or `OUTPUT_VARIABLE` options only if really required. Using them will require that when cross-compiling, the cache variables will have to be set manually to the output of the executable. You can also "guard" the calls to `try_run` with an `if()` block checking the `CMAKE_CROSSCOMPILING` variable and provide an easy-to-preset alternative for this case.