cc -pthread   -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations sys_socket/SO_DOMAIN.c -o sys_socket/SO_DOMAIN -D_POSIX_C_SOURCE=202405L  -lm -lpthread   -liconv
sys_socket/SO_DOMAIN.c:2:17: error: use of undeclared identifier 'SO_DOMAIN'
    2 | int const foo = SO_DOMAIN;
      |                 ^~~~~~~~~
1 error generated.