clang -O2  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations sys_mman/O_RDONLY.c -o sys_mman/O_RDONLY -D_POSIX_C_SOURCE=202405L  -lm  -lintl
sys_mman/O_RDONLY.c:3:17: error: use of undeclared identifier 'O_RDONLY'
int const foo = O_RDONLY;
                ^
1 error generated.