CMake/Modules/CheckStructHasMember.cmake

# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
# file Copyright.txt or https://cmake.org/licensing for details.

#[=======================================================================[.rst:
CheckStructHasMember
--------------------

Check if the given struct or class has the specified member variable

.. command:: CHECK_STRUCT_HAS_MEMBER

  .. code-block:: cmake

    CHECK_STRUCT_HAS_MEMBER(<struct> <member> <header> <variable>
                            [LANGUAGE <language>])

  ::

    <struct> - the name of the struct or class you are interested in
    <member> - the member which existence you want to check
    <header> - the header(s) where the prototype should be declared
    <variable> - variable to store the result
    <language> - the compiler to use (C or CXX)



The following variables may be set before calling this macro to modify
the way the check is run:

::

  CMAKE_REQUIRED_FLAGS = string of compile command line flags
  CMAKE_REQUIRED_DEFINITIONS = list of macros to define (-DFOO=bar)
  CMAKE_REQUIRED_INCLUDES = list of include directories
  CMAKE_REQUIRED_LINK_OPTIONS = list of options to pass to link command
  CMAKE_REQUIRED_LIBRARIES = list of libraries to link
  CMAKE_REQUIRED_QUIET = execute quietly without messages


Example:

.. code-block:: cmake

  CHECK_STRUCT_HAS_MEMBER("struct timeval" tv_sec sys/select.h
                          HAVE_TIMEVAL_TV_SEC LANGUAGE C)
#]=======================================================================]

include_guard(GLOBAL)
include(CheckCSourceCompiles)
include(CheckCXXSourceCompiles)

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 "
${_INCLUDE_FILES}
int main()
{
  (void)sizeof(((${_STRUCT} *)0)->${_MEMBER});
  return 0;
}
")

  if("${_lang}" STREQUAL "C")
    CHECK_C_SOURCE_COMPILES("${_CHECK_STRUCT_MEMBER_SOURCE_CODE}" ${_RESULT})
  elseif("${_lang}" STREQUAL "CXX")
    CHECK_CXX_SOURCE_COMPILES("${_CHECK_STRUCT_MEMBER_SOURCE_CODE}" ${_RESULT})
  else()
    message(FATAL_ERROR "Unknown language:\n  ${_lang}\nSupported languages: C, CXX.\n")
  endif()
endmacro ()