1function(check_lto)
2    if (DEFINED LTO_WORKS)
3        return()
4    endif()
5
6    set(LTO_WORKS FALSE CACHE INTERNAL "LTO works")
7
8    CHECK_CXX_COMPILER_FLAG("-flto" HAS_LTO_FLAG)
9
10    if (NOT HAS_LTO_FLAG)
11        return()
12    endif()
13
14    find_program(LTO_AR NAMES "${CMAKE_C_COMPILER}-ar" gcc-ar)
15    find_program(LTO_RANLIB NAMES "${CMAKE_C_COMPILER}-ranlib" gcc-ranlib)
16
17    if (NOT LTO_AR OR NOT LTO_RANLIB)
18        return()
19    endif()
20
21    EXECUTE_PROCESS(COMMAND "${LTO_AR}" --version RESULT_VARIABLE ret OUTPUT_QUIET ERROR_QUIET)
22    if (ret)
23        return()
24    endif()
25
26    EXECUTE_PROCESS(COMMAND "${LTO_RANLIB}" --version RESULT_VARIABLE ret OUTPUT_QUIET ERROR_QUIET)
27    if (ret)
28        return()
29    endif()
30
31    set(LTO_WORKS TRUE CACHE INTERNAL "LTO works")
32endfunction()
33