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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:
CheckStructHasMember
--------------------
This module provides a command to check whether a struct or class has a
specified member variable.
Load this module in a CMake project with:
.. code-block:: cmake
include(CheckStructHasMember)
Commands
^^^^^^^^
This module provides the following command:
.. command:: check_struct_has_member
Checks once if the given struct or class has the specified member variable:
.. code-block:: cmake
check_struct_has_member(
<struct>
<member>
<headers>
<variable>
[LANGUAGE <language>]
)
This command checks once whether the struct or class ``<struct>`` contains
the specified ``<member>`` after including the given header(s) ``<headers>``
where the prototype should be declared. Multiple header files can be
specified in one argument as a string using a :ref:`semicolon-separated list
<CMake Language Lists>`. The result is stored in an internal cache variable
``<variable>``.
The options are:
``LANGUAGE <language>``
Use the ``<language>`` compiler to perform the check.
Acceptable values are ``C`` and ``CXX``.
If not specified, it defaults to ``C``.
.. 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
^^^^^^^^
Example: Checking C Struct Member
"""""""""""""""""""""""""""""""""
In the following example, this module checks if the C struct ``timeval`` has
a member variable ``tv_sec`` after including the ``<sys/select.h>`` header.
The result of the check is stored in the internal cache variable
``HAVE_TIMEVAL_TV_SEC``.
.. code-block:: cmake
include(CheckStructHasMember)
check_struct_has_member(
"struct timeval"
tv_sec
sys/select.h
HAVE_TIMEVAL_TV_SEC
)
Example: Checking C++ Struct Member
"""""""""""""""""""""""""""""""""""
In the following example, this module checks if the C++ struct ``std::tm``
has a member variable ``tm_gmtoff`` after including the ``<ctime>`` header.
The result of the check is stored in the internal cache variable
``HAVE_TM_GMTOFF``.
.. code-block:: cmake
include(CheckStructHasMember)
check_struct_has_member(
std::tm
tm_gmtoff
ctime
HAVE_TM_GMTOFF
LANGUAGE CXX
)
Example: Isolated Check With Compile Definitions
""""""""""""""""""""""""""""""""""""""""""""""""
In the following example, the check is performed with temporarily modified
compile definitions using the :module:`CMakePushCheckState` module:
.. code-block:: cmake
include(CheckStructHasMember)
include(CMakePushCheckState)
cmake_push_check_state(RESET)
set(CMAKE_REQUIRED_DEFINITIONS -D_GNU_SOURCE)
check_struct_has_member(
"struct utsname"
domainname
sys/utsname.h
HAVE_UTSNAME_DOMAINNAME
)
cmake_pop_check_state()
#]=======================================================================]
include_guard(GLOBAL)
include(CheckSourceCompiles)
macro (CHECK_STRUCT_HAS_MEMBER _STRUCT _MEMBER _HEADER _RESULT)
set(_INCLUDE_FILES)
foreach (it ${_HEADER})
string(APPEND _INCLUDE_FILES "#include <${it}>\n")
endforeach ()
if("x${ARGN}" STREQUAL "x")
set(_lang C)
elseif("x${ARGN}" MATCHES "^xLANGUAGE;([a-zA-Z]+)$")
set(_lang "${CMAKE_MATCH_1}")
else()
message(FATAL_ERROR "Unknown arguments:\n ${ARGN}\n")
endif()
set(_CHECK_STRUCT_MEMBER_SOURCE_CODE "
${_INCLUDE_FILES}
int main(void)
{
(void)sizeof(((${_STRUCT} *)0)->${_MEMBER});
return 0;
}
")
if("${_lang}" STREQUAL "C")
check_source_compiles(C "${_CHECK_STRUCT_MEMBER_SOURCE_CODE}" ${_RESULT})
elseif("${_lang}" STREQUAL "CXX")
check_source_compiles(CXX "${_CHECK_STRUCT_MEMBER_SOURCE_CODE}" ${_RESULT})
else()
message(FATAL_ERROR "Unknown language:\n ${_lang}\nSupported languages: C, CXX.\n")
endif()
endmacro ()
# FIXME(#24994): The following modules are included only for compatibility
# with projects that accidentally relied on them with CMake 3.26 and below.
include(CheckCSourceCompiles)
include(CheckCXXSourceCompiles)
|
