cc -O2 -pipe  -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations termios/CRDLY.c -o termios/CRDLY -D_POSIX_C_SOURCE=202405L  -lm -lpthread 
termios/CRDLY.c:8:17: error: use of undeclared identifier 'CRDLY'
int const foo = CRDLY;
                ^
1 error generated.