cc -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations sys_wait/union-sigval.c -o sys_wait/union-sigval -D_POSIX_C_SOURCE=202405L -lm -lpthread -lrt -lintl -liconv
sys_wait/union-sigval.c:2:14: error: storage size of ‘foo’ isn’t known
    2 | union sigval foo;
      |              ^~~