cc -O2 -pipe  -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations fcntl/O_EXEC.c -o fcntl/O_EXEC -D_POSIX_C_SOURCE=202405L  -lm -lpthread 
fcntl/O_EXEC.c:3:2: error: "O_EXEC is not defined"
#error "O_EXEC is not defined"
 ^
1 error generated.