/in/foo.c: In function 'main':
/in/foo.c:12:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(s1);
  ^~~~
In file included from /in/foo.c:1:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.c:32:7: warning: implicit declaration of function 'stricmp' [-Wimplicit-function-declaration]
   if (stricmp(s3, s4) == 0)
       ^~~~~~~
/tmp/cc0yMoFe.o: In function `main':
foo.c:(.text.startup+0x2b): warning: the `gets' function is dangerous and should not be used.
foo.c:(.text.startup+0x15c): undefined reference to `stricmp'
collect2: error: ld returned 1 exit status