/in/foo.c: In function 'HWS':
/in/foo.c:7:2: warning: implicit declaration of function '_itoa_s' [-Wimplicit-function-declaration]
  _itoa_s(n, a, 10);
  ^~~~~~~
/tmp/cc4VB5uw.o: In function `HWS':
foo.c:(.text+0x13): undefined reference to `_itoa_s'
/tmp/cc4VB5uw.o: In function `XFS':
foo.c:(.text+0xe3): undefined reference to `_itoa_s'
collect2: error: ld returned 1 exit status