cmake_minimum_required (VERSION 2.6)

project(IncludeDirectoriesCPATH)
message(STATUS "CPATH: $ENV{CPATH}")
message(STATUS "impC: ${CMAKE_C_IMPLICIT_INCLUDE_DIRECTORIES}")
message(STATUS "impX: ${CMAKE_CXX_IMPLICIT_INCLUDE_DIRECTORIES}")

if (((CMAKE_C_COMPILER_ID STREQUAL GNU AND CMAKE_C_COMPILER_VERSION VERSION_GREATER 4.4)
    OR (CMAKE_C_COMPILER_ID STREQUAL Clang AND NOT "x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC") OR CMAKE_C_COMPILER_ID STREQUAL AppleClang)
    AND (CMAKE_GENERATOR STREQUAL "Unix Makefiles"
      OR CMAKE_GENERATOR STREQUAL "Ninja"
      OR (CMAKE_GENERATOR STREQUAL "Xcode" AND NOT XCODE_VERSION VERSION_LESS 6.0)))
  include(CheckCXXCompilerFlag)
  check_cxx_compiler_flag(-Wunused-variable run_sys_includes_test)
  if(run_sys_includes_test)
    # The Bullseye wrapper appears to break the -isystem effect.
    execute_process(COMMAND ${CMAKE_CXX_COMPILER} --version OUTPUT_VARIABLE out ERROR_VARIABLE out)
    if("x${out}" MATCHES "Bullseye")
      set(run_sys_includes_test 0)
    endif()
  endif()
  if (run_sys_includes_test)
    add_subdirectory(SystemIncludeDirectories)
  endif()
endif()
