TestForSTDNamespace — CMake 4.3.0 Documentation

# TestForSTDNamespace

This module checks whether the `CXX` compiler supports the `std` namespace for the C++ Standard Library.

Load this module in a CMake project with:

    include(TestForSTDNamespace)

Early versions of C++ (pre-C++98) did not have a requirement for a dedicated namespace of C++ Standard Template Library (STL) components (e.g. `list`, etc.) and other parts of the C++ Standard Library (such as I/O streams `cout`, `endl`, etc), so they were available globally.

This module defines the following cache variable:

`CMAKE_NO_STD_NAMESPACE`

  A cache variable containing the result of the check. It will be set to value `0` if the `std` namespace is supported (`C++ 98` and newer), and to value `1` if not (`ANSI C++`).

Note

The `std` namespace got formally introduced in `C++ 98` standard, making this issue obsolete.

## Examples

Including this module will check for the `std` namespace support and define the `CMAKE_NO_STD_NAMESPACE` cache variable:

`CMakeLists.txt`

    include(TestForSTDNamespace)
    file(
      CONFIGURE
      OUTPUT config.h
      CONTENT "#cmakedefine CMAKE_NO_STD_NAMESPACE"
    )

which can be then used in a C++ program to define the missing namespace:

`example.cxx`

    #include "config.h"

    #ifdef CMAKE_NO_STD_NAMESPACE
    #  define std
    #endif

## See Also

- The `CMakeBackwardCompatibilityCXX` module.