#.rst:
# SgGNUSource
# -----------
#
# `_GNU_SOURCE` checking.
#
# Checks if `_GNU_SOURCE` is available.
#
# ::
#
# _GNU_SOURCE - True if `_GNU_SOURCE` is available. If so, a `-D_GNU_SOURCE` is
# declared too.

#                         _
#   ___  __ _  __ _ _   _(_)
#  / __|/ _` |/ _` | | | | |
#  \__ \ (_| | (_| | |_| | |
#  |___/\__,_|\__, |\__,_|_|
#             |___/
#
# Cross-platform library which helps to develop web servers or frameworks.
#
# Copyright (C) 2016-2019 Silvio Clecio <silvioprog@gmail.com>
#
# Sagui library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# Sagui library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with Sagui library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
#

if(__SG_GNU_SOURCE_INCLUDED)
  return()
endif()
set(__SG_GNU_SOURCE_INCLUDED ON)

include(CheckSymbolExists)

if(NOT _GNU_SOURCE)
  check_symbol_exists(__GNU_LIBRARY__ "features.h" _GNU_SOURCE)

  if(NOT _GNU_SOURCE)
    unset(_GNU_SOURCE CACHE)
    check_symbol_exists(_GNU_SOURCE "features.h" _GNU_SOURCE)
  endif()
endif()

if(_GNU_SOURCE)
  add_definitions(-D_GNU_SOURCE)
endif()