/in/foo.c: In function 'main':
/in/foo.c:16:4: warning: implicit declaration of function 'scanf_s' [-Wimplicit-function-declaration]
    scanf_s("%d %d %d", &year, &month, &day);
    ^~~~~~~
/tmp/ccN809Qa.o: In function `main':
foo.c:(.text.startup+0x93): undefined reference to `scanf_s'
collect2: error: ld returned 1 exit status