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58e8999c28
- Added intro code blocks showing how to include these modules. - Added section titles. - Used "command" instead of "macro". - Indented command-related descriptions according to the command section indentation level. - Added the "See Also" sections. - Synced descriptions between the modules.
107 lines
3.5 KiB
CMake
107 lines
3.5 KiB
CMake
# Distributed under the OSI-approved BSD 3-Clause License. See accompanying
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# file LICENSE.rst or https://cmake.org/licensing for details.
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#[=======================================================================[.rst:
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CheckCXXSymbolExists
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--------------------
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This module provides a command to check whether a C++ symbol exists.
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Load this module in a CMake project with:
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.. code-block:: cmake
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include(CheckCXXSymbolExists)
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Commands
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^^^^^^^^
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This module provides the following command:
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.. command:: check_cxx_symbol_exists
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Checks once whether a symbol exists as a function, variable, or preprocessor
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macro in C++:
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.. code-block:: cmake
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check_cxx_symbol_exists(<symbol> <headers> <variable>)
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This command checks whether the ``<symbol>`` is available after including
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the specified header file(s) ``<headers>``, and stores the result in the
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internal cache variable ``<variable>``. Multiple header files can be
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specified in one argument as a string using a
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:ref:`semicolon-separated list <CMake Language Lists>`.
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If the header files define the symbol as a macro, it is considered
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available and assumed to work. If the symbol is declared as a function
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or variable, the check also ensures that it links successfully
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(i.e., the symbol must exist in a linked library or object file).
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Symbols that are types, enum values, or C++ templates are not
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recognized. For those, consider using the :module:`CheckTypeSize` or
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:module:`CheckSourceCompiles` module instead.
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This command is intended to check symbols as they appear in C++. For C
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symbols, use the :module:`CheckSymbolExists` module instead.
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.. note::
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This command is unreliable for symbols that are (potentially) overloaded
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functions. Since there is no reliable way to predict whether
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a given function in the system environment may be defined as an
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overloaded function or may be an overloaded function on other systems
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or will become so in the future, it is generally advised to use the
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:module:`CheckSourceCompiles` module for checking any function symbol
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(unless it is certain the checked function is not overloaded on other
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systems or will not be so in the future).
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.. rubric:: Variables Affecting the Check
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The following variables may be set before calling this command to modify
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the way the check is run:
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.. include:: /module/include/CMAKE_REQUIRED_FLAGS.rst
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.. include:: /module/include/CMAKE_REQUIRED_DEFINITIONS.rst
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.. include:: /module/include/CMAKE_REQUIRED_INCLUDES.rst
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.. include:: /module/include/CMAKE_REQUIRED_LINK_OPTIONS.rst
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.. include:: /module/include/CMAKE_REQUIRED_LIBRARIES.rst
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.. include:: /module/include/CMAKE_REQUIRED_LINK_DIRECTORIES.rst
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.. include:: /module/include/CMAKE_REQUIRED_QUIET.rst
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Examples
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^^^^^^^^
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The following example demonstrates how to check for the presence of a
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preprocessor macro ``SEEK_SET`` and the C++ function ``std::fopen()`` from
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the ``<cstdio>`` header using this module:
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.. code-block:: cmake
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include(CheckCXXSymbolExists)
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# Check for macro SEEK_SET
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check_cxx_symbol_exists(SEEK_SET "cstdio" HAVE_SEEK_SET)
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# Check for function std::fopen
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check_cxx_symbol_exists(std::fopen "cstdio" HAVE_STD_FOPEN)
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See Also
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^^^^^^^^
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* The :module:`CheckSymbolExists` module to check whether a C symbol exists.
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#]=======================================================================]
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include_guard(GLOBAL)
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include(CheckSymbolExists)
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macro(CHECK_CXX_SYMBOL_EXISTS SYMBOL FILES VARIABLE)
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__CHECK_SYMBOL_EXISTS_IMPL(CheckSymbolExists.cxx "${SYMBOL}" "${FILES}" "${VARIABLE}" )
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endmacro()
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