cc -O2 -pipe  -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations termios/NL1.c -o termios/NL1 -D_POSIX_C_SOURCE=202405L  -lm -lpthread 
termios/NL1.c:8:17: error: use of undeclared identifier 'NL1'
int const foo = NL1;
                ^
1 error generated.