Error(s):

source_file.cpp:12:5: error: anonymous structs are a GNU extension [-Werror,-Wgnu-anonymous-struct]
    struct {    // Function parameters
    ^
source_file.cpp:16:5: error: anonymous structs are a GNU extension [-Werror,-Wgnu-anonymous-struct]
    struct {    // Function return value
    ^
source_file.cpp:28:9: error: designated initializers are a C99 feature [-Werror,-Wc99-extensions]
        .array = array_1,
        ^~~~~~~~~~~~~~~~
source_file.cpp:29:9: error: designated initializers are a C99 feature [-Werror,-Wc99-extensions]
        .size = ARRAY_COUNT(array_1),
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
source_file.cpp:24:16: warning: unused variable 'ret2' [-Wunused-variable]
    int  ret1, ret2;
               ^
source_file.cpp:27:13: warning: unused variable 'param' [-Wunused-variable]
    Param_u param = {
            ^
source_file.cpp:24:10: warning: unused variable 'ret1' [-Wunused-variable]
    int  ret1, ret2;
         ^
3 warnings and 4 errors generated.