try_run

• Try Compiling and Running Source Files
• Other Behavior Settings
• Behavior when Cross Compiling

Try compiling and then running some code.

Try Compiling and Running Source Files

try_run(RUN_RESULT_VAR COMPILE_RESULT_VAR
        bindir srcfile [CMAKE_FLAGS <flags>...]
        [COMPILE_DEFINITIONS <defs>...]
        [LINK_LIBRARIES <libs>...]
        [COMPILE_OUTPUT_VARIABLE <var>]
        [RUN_OUTPUT_VARIABLE <var>]
        [OUTPUT_VARIABLE <var>]
        [ARGS <args>...])

Try compiling a <srcfile>. Returns TRUE or FALSE for success or failure in COMPILE_RESULT_VAR. If the compile succeeded, runs the executable and returns its exit code in RUN_RESULT_VAR. If the executable was built, but failed to run, then RUN_RESULT_VAR will be set to FAILED_TO_RUN. See the try_compile() command for information on how the test project is constructed to build the source file.

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 example in try_compile() 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.

COMPILE_OUTPUT_VARIABLE <var>

Report the compile step build output in a given variable.

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>

Report the compile build output and the output from running the executable in the given variable. This option exists for legacy reasons. Prefer COMPILE_OUTPUT_VARIABLE and RUN_OUTPUT_VARIABLE instead.

RUN_OUTPUT_VARIABLE <var>

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

Other Behavior Settings

Set the CMAKE_TRY_COMPILE_CONFIGURATION variable to choose a build configuration.

Behavior when Cross Compiling

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:

<RUN_RESULT_VAR>

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

<RUN_RESULT_VAR>__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.

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_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.