cc -O2 -pipe -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations time/daylight.c -o time/daylight -D_POSIX_C_SOURCE=202405L  -lm -lpthread -lrt  -lstdthreads -lcrypt
time/daylight.c:8:13: error: use of undeclared identifier 'daylight'
    8 | int *foo = &daylight;
      |             ^
1 error generated.