cc -O2 -pipe  -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations semaphore/struct-timespec.c -o semaphore/struct-timespec -D_POSIX_C_SOURCE=202405L  -lm -lpthread 
semaphore/struct-timespec.c:2:17: error: tentative definition has type 'struct timespec' that is never completed
struct timespec foo;
                ^
/usr/include/semaphore.h:45:8: note: forward declaration of 'struct timespec'
struct timespec;
       ^
1 error generated.