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# Distributed under the OSI-approved BSD 3-Clause License. See accompanying
# file LICENSE.rst or https://cmake.org/licensing for details.
#[=======================================================================[.rst:
CheckCXXSymbolExists
--------------------
This module provides a command to check whether a C++ symbol exists.
Load this module in a CMake project with:
.. code-block:: cmake
include(CheckCXXSymbolExists)
Commands
^^^^^^^^
This module provides the following command:
.. command:: check_cxx_symbol_exists
Checks once whether a symbol exists as a function, variable, or preprocessor
macro in C++:
.. code-block:: cmake
check_cxx_symbol_exists(<symbol> <headers> <variable>)
This command checks whether the ``<symbol>`` is available after including
the specified header file(s) ``<headers>``, and stores the result in the
internal cache variable ``<variable>``. Multiple header files can be
specified in one argument as a string using a
:ref:`semicolon-separated list <CMake Language Lists>`.
If the header files define the symbol as a macro, it is considered
available and assumed to work. If the symbol is declared as a function
or variable, the check also ensures that it links successfully
(i.e., the symbol must exist in a linked library or object file).
Symbols that are types, enum values, or C++ templates are not
recognized. For those, consider using the :module:`CheckTypeSize` or
:module:`CheckSourceCompiles` module instead.
This command is intended to check symbols as they appear in C++. For C
symbols, use the :module:`CheckSymbolExists` module instead.
.. note::
This command is unreliable for symbols that are (potentially) overloaded
functions. Since there is no reliable way to predict whether
a given function in the system environment may be defined as an
overloaded function or may be an overloaded function on other systems
or will become so in the future, it is generally advised to use the
:module:`CheckSourceCompiles` module for checking any function symbol
(unless it is certain the checked function is not overloaded on other
systems or will not be so in the future).
.. rubric:: Variables Affecting the Check
The following variables may be set before calling this command to modify
the way the check is run:
.. include:: /module/include/CMAKE_REQUIRED_FLAGS.rst
.. include:: /module/include/CMAKE_REQUIRED_DEFINITIONS.rst
.. include:: /module/include/CMAKE_REQUIRED_INCLUDES.rst
.. include:: /module/include/CMAKE_REQUIRED_LINK_OPTIONS.rst
.. include:: /module/include/CMAKE_REQUIRED_LIBRARIES.rst
.. include:: /module/include/CMAKE_REQUIRED_LINK_DIRECTORIES.rst
.. include:: /module/include/CMAKE_REQUIRED_QUIET.rst
Examples
^^^^^^^^
The following example demonstrates how to check for the presence of a
preprocessor macro ``SEEK_SET`` and the C++ function ``std::fopen()`` from
the ``<cstdio>`` header using this module:
.. code-block:: cmake
include(CheckCXXSymbolExists)
# Check for macro SEEK_SET
check_cxx_symbol_exists(SEEK_SET "cstdio" HAVE_SEEK_SET)
# Check for function std::fopen
check_cxx_symbol_exists(std::fopen "cstdio" HAVE_STD_FOPEN)
See Also
^^^^^^^^
* The :module:`CheckSymbolExists` module to check whether a C symbol exists.
#]=======================================================================]
include_guard(GLOBAL)
include(CheckSymbolExists)
macro(CHECK_CXX_SYMBOL_EXISTS SYMBOL FILES VARIABLE)
__CHECK_SYMBOL_EXISTS_IMPL(CheckSymbolExists.cxx "${SYMBOL}" "${FILES}" "${VARIABLE}" )
endmacro()
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