cc -O2 -pipe -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations fcntl/struct-f_owner_ex.c -o fcntl/struct-f_owner_ex -D_POSIX_C_SOURCE=202405L  -lm -lpthread -lrt  -lstdthreads -lcrypt
fcntl/struct-f_owner_ex.c:2:19: error: tentative definition has type 'struct f_owner_ex' that is never completed
    2 | struct f_owner_ex foo;
      |                   ^
fcntl/struct-f_owner_ex.c:2:8: note: forward declaration of 'struct f_owner_ex'
    2 | struct f_owner_ex foo;
      |        ^
1 error generated.