foo.c: In function 'main':
foo.c:11:2: warning: implicit declaration of function 'gets_s'; did you mean 'gets'? [-Wimplicit-function-declaration]
   11 |  gets_s(a);
      |  ^~~~~~
      |  gets
foo.c:8:9: warning: unused variable 'o' [-Wunused-variable]
    8 |  int n, o = 0;
      |         ^
foo.c:10:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   10 |  scanf("%d ", &n);
      |  ^~~~~~~~~~~~~~~~
/usr/bin/ld: /tmp/ccce7aIx.o: in function `main':
foo.c:(.text.startup+0x44): undefined reference to `gets_s'
collect2: error: ld returned 1 exit status

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