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TestForSTDNamespace: Update documentation

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This describes the module in more details to make upgrading code easier.
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Peter Kokot 2025-03-11 15:28:48 +01:00
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Modules/TestForSTDNamespace.cmake
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@ -5,13 +5,48 @@
TestForSTDNamespace
-------------------
Test for std:: namespace support
This module checks whether the ``CXX`` compiler supports the ``std`` namespace
for the C++ Standard Library. 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.
check if the compiler supports std:: on stl classes
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++``).
CMAKE_NO_STD_NAMESPACE - defined by the results
.. 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:
.. code-block:: cmake
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:
.. code-block:: c++
#include "config.h"
#ifdef CMAKE_NO_STD_NAMESPACE
# define std
#endif
#]=======================================================================]
if(NOT DEFINED CMAKE_STD_NAMESPACE)