diff options
Diffstat (limited to 'Modules/CheckCXXSymbolExists.cmake')
-rw-r--r-- | Modules/CheckCXXSymbolExists.cmake | 39 |
1 files changed, 31 insertions, 8 deletions
diff --git a/Modules/CheckCXXSymbolExists.cmake b/Modules/CheckCXXSymbolExists.cmake index 2cccd09ff..5c9079dbf 100644 --- a/Modules/CheckCXXSymbolExists.cmake +++ b/Modules/CheckCXXSymbolExists.cmake @@ -5,26 +5,38 @@ CheckCXXSymbolExists -------------------- -Check if a symbol exists as a function, variable, or macro in C++ +Check if a symbol exists as a function, variable, or macro in ``C++``. -.. command:: CHECK_CXX_SYMBOL_EXISTS +.. command:: check_cxx_symbol_exists .. code-block:: cmake - CHECK_CXX_SYMBOL_EXISTS(<symbol> <files> <variable>) + check_cxx_symbol_exists(<symbol> <files> <variable>) Check that the ``<symbol>`` is available after including given header ``<files>`` and store the result in a ``<variable>``. Specify the list of files in one argument as a semicolon-separated list. - ``CHECK_CXX_SYMBOL_EXISTS()`` can be used to check in C++ files, as - opposed to ``CHECK_SYMBOL_EXISTS()``, which works only for ``C``. + ``check_cxx_symbol_exists()`` can be used to check for symbols as seen by + the C++ compiler, as opposed to :command:`check_symbol_exists`, which always + uses the ``C`` compiler. If the header files define the symbol as a macro it is considered available and assumed to work. If the header files declare the symbol as a function or variable then the symbol must also be available for - linking. If the symbol is a type or enum value it will not be - recognized (consider using :module:`CheckTypeSize` - or :module:`CheckCXXSourceCompiles`). + linking. If the symbol is a type, enum value, or C++ template it will + not be recognized: consider using the :module:`CheckTypeSize` + or :module:`CheckCXXSourceCompiles` module instead. + +.. note:: + + This command is unreliable when ``<symbol>`` is (potentially) an overloaded + function. 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:`CheckCXXSourceCompiles` module for + checking any function symbol (unless somehow you surely know the checked + function is not overloaded on other systems or will not be so in the + future). The following variables may be set before calling this macro to modify the way the check is run: @@ -43,6 +55,17 @@ the way the check is run: command. See policy :policy:`CMP0075`. ``CMAKE_REQUIRED_QUIET`` execute quietly without messages. + +For example: + +.. 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) #]=======================================================================] include_guard(GLOBAL) |