# CheckCXXSourceRuns

This module provides a command to check whether a C++ source can be built and run.

Load this module in a CMake project with:

    include(CheckCXXSourceRuns)

## Commands

This module provides the following command:

check_cxx_source_runs

  Checks once whether the given C++ source code compiles and links into an executable that can subsequently be run:

      check_cxx_source_runs(<code> <variable>)

  The C++ source supplied in `<code>` must contain at least a `main()` function. The result of the check is stored in the internal cache variable specified by `<variable>`. If the code builds and runs with exit code `0`, success is indicated by a boolean true value. Failure to build or run is indicated by a boolean false value, such as an empty string or an error message.

  Variables Affecting the Check

  The following variables may be set before calling this command to modify the way the check is run:

  `CMAKE_REQUIRED_FLAGS`

    A space-separated string of additional flags to pass to the compiler. A semicolon-separated list will not work. The contents of `CMAKE_<LANG>_FLAGS` and its associated configuration-specific `CMAKE_<LANG>_FLAGS_<CONFIG>` variables are automatically prepended to the compiler command before the contents of this variable.

  `CMAKE_REQUIRED_DEFINITIONS`

    A semicolon-separated list of compiler definitions, each of the form `-DFOO` or `-DFOO=bar`. A definition for the name specified by the result variable argument of the check command is also added automatically.

  `CMAKE_REQUIRED_INCLUDES`

    A semicolon-separated list of header search paths to pass to the compiler. These will be the only header search paths used; the contents of the `INCLUDE_DIRECTORIES` directory property will be ignored.

  `CMAKE_REQUIRED_LINK_OPTIONS`

    Added in version 3.14.

    A semicolon-separated list of options to add to the link command (see `try_compile()` for further details).

  `CMAKE_REQUIRED_LIBRARIES`

    A semicolon-separated list of libraries to add to the link command. These can be the names of system libraries, or they can be Imported Targets (see `try_compile()` for further details).

  `CMAKE_REQUIRED_LINK_DIRECTORIES`

    Added in version 3.31.

    A semicolon-separated list of library search paths to pass to the linker (see `try_compile()` for further details).

  `CMAKE_REQUIRED_QUIET`

    Added in version 3.1.

    If this variable evaluates to a boolean true value, all status messages associated with the check will be suppressed.

## Examples

The following example demonstrates how to check whether the C++ standard library is functional and `std::vector` works at runtime. If the source compiles, links, and runs successfully, internal cache variable `HAVE_WORKING_STD_VECTOR` will be set to boolean true value. Code is supplied using Bracket Argument for easier embedded quotes handling:

    include(CheckCXXSourceRuns)

    check_cxx_source_runs([[
      #include <iostream>
      #include <vector>

      int main()
      {
        std::vector<int> v = {1, 2, 3};
        if (v.size() != 3) return 1;
        std::cout << "Vector works correctly." << std::endl;
        return 0;
      }
    ]] HAVE_WORKING_STD_VECTOR)

## See Also

- The `CheckSourceRuns` module for a more general command syntax.

- The `CheckSourceCompiles` module to check whether a source code can be built.