/in/foo.c: In function 'main':
/in/foo.c:5:2: warning: implicit declaration of function 'gets' [-Wimplicit-function-declaration]
  gets(s1);
  ^~~~
/in/foo.c:8:2: warning: implicit declaration of function 'puts' [-Wimplicit-function-declaration]
  puts(s1);
  ^~~~
/tmp/ccTjlQE4.o: In function `main':
foo.c:(.text.startup+0x3a): warning: the `gets' function is dangerous and should not be used.