clang -O2  -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  -lintl
In file included from sys_wait/union-sigval.c:1:
/usr/include/sys/wait.h:175:1: error: unknown type name 'pid_t'
pid_t   wait(int *);
^
/usr/include/sys/wait.h:176:1: error: unknown type name 'pid_t'
pid_t   waitpid(pid_t, int *, int);
^
/usr/include/sys/wait.h:176:22: error: expected identifier
pid_t   waitpid(pid_t, int *, int);
                       ^
sys_wait/union-sigval.c:2:14: error: tentative definition has type 'union sigval' that is never completed
union sigval foo;
             ^
sys_wait/union-sigval.c:2:7: note: forward declaration of 'union sigval'
union sigval foo;
      ^
4 errors generated.