cc -pipe -O   -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations sys_mman/O_RDWR.c -o sys_mman/O_RDWR -D_POSIX_C_SOURCE=202405L  -lm -lpthread -lrt  -lrt -lcrypt
sys_mman/O_RDWR.c:3:17: error: 'O_RDWR' undeclared here (not in a function)
 int const foo = O_RDWR;
                 ^~~~~~