foo.c: In function 'main':
foo.c:8:2: warning: implicit declaration of function 'gets_s'; did you mean 'gets'? [-Wimplicit-function-declaration]
  gets_s(a);
  ^~~~~~
  gets
foo.c:10:2: warning: implicit declaration of function 'scanf_s'; did you mean 'scanf'? [-Wimplicit-function-declaration]
  scanf_s("%d", &k);
  ^~~~~~~
  scanf
/tmp/ccVr0ft7.o: In function `main':
foo.c:(.text.startup+0x24): undefined reference to `gets_s'
foo.c:(.text.startup+0x37): undefined reference to `scanf_s'
collect2: error: ld returned 1 exit status

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