1# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
2# file Copyright.txt or https://cmake.org/licensing for details.
3
4#[=======================================================================[.rst:
5CheckCXXSymbolExists
6--------------------
7
8Check if a symbol exists as a function, variable, or macro in ``C++``.
9
10.. command:: check_cxx_symbol_exists
11
12  .. code-block:: cmake
13
14    check_cxx_symbol_exists(<symbol> <files> <variable>)
15
16  Check that the ``<symbol>`` is available after including given header
17  ``<files>`` and store the result in a ``<variable>``.  Specify the list of
18  files in one argument as a semicolon-separated list.
19  ``check_cxx_symbol_exists()`` can be used to check for symbols as seen by
20  the C++ compiler, as opposed to :command:`check_symbol_exists`, which always
21  uses the ``C`` compiler.
22
23  If the header files define the symbol as a macro it is considered
24  available and assumed to work.  If the header files declare the symbol
25  as a function or variable then the symbol must also be available for
26  linking.  If the symbol is a type, enum value, or C++ template it will
27  not be recognized: consider using the :module:`CheckTypeSize`
28  or :module:`CheckSourceCompiles` module instead.
29
30.. note::
31
32  This command is unreliable when ``<symbol>`` is (potentially) an overloaded
33  function. Since there is no reliable way to predict whether a given function
34  in the system environment may be defined as an overloaded function or may be
35  an overloaded function on other systems or will become so in the future, it
36  is generally advised to use the :module:`CheckCXXSourceCompiles` module for
37  checking any function symbol (unless somehow you surely know the checked
38  function is not overloaded on other systems or will not be so in the
39  future).
40
41The following variables may be set before calling this macro to modify
42the way the check is run:
43
44``CMAKE_REQUIRED_FLAGS``
45  string of compile command line flags.
46``CMAKE_REQUIRED_DEFINITIONS``
47  a :ref:`;-list <CMake Language Lists>` of macros to define (-DFOO=bar).
48``CMAKE_REQUIRED_INCLUDES``
49  a :ref:`;-list <CMake Language Lists>` of header search paths to pass to
50  the compiler.
51``CMAKE_REQUIRED_LINK_OPTIONS``
52  .. versionadded:: 3.14
53    a :ref:`;-list <CMake Language Lists>` of options to add to the link command.
54``CMAKE_REQUIRED_LIBRARIES``
55  a :ref:`;-list <CMake Language Lists>` of libraries to add to the link
56  command. See policy :policy:`CMP0075`.
57``CMAKE_REQUIRED_QUIET``
58  .. versionadded:: 3.1
59    execute quietly without messages.
60
61For example:
62
63.. code-block:: cmake
64
65  include(CheckCXXSymbolExists)
66
67  # Check for macro SEEK_SET
68  check_cxx_symbol_exists(SEEK_SET "cstdio" HAVE_SEEK_SET)
69  # Check for function std::fopen
70  check_cxx_symbol_exists(std::fopen "cstdio" HAVE_STD_FOPEN)
71#]=======================================================================]
72
73include_guard(GLOBAL)
74include(CheckSymbolExists)
75
76macro(CHECK_CXX_SYMBOL_EXISTS SYMBOL FILES VARIABLE)
77  __CHECK_SYMBOL_EXISTS_IMPL("${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/CheckSymbolExists.cxx" "${SYMBOL}" "${FILES}" "${VARIABLE}" )
78endmacro()
79