/in/foo.c: In function 'compute':
/in/foo.c:42:5: warning: 'gets' is deprecated [-Wdeprecated-declarations]
     gets(buf);
     ^~~~
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:110:20: warning: array subscript has type 'char' [-Wchar-subscripts]
             instack[stack[top]] = 0;
                    ^
/in/foo.c:123:9: warning: 'gets' is deprecated [-Wdeprecated-declarations]
         gets(buf);
         ^~~~
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: In function 'main':
/in/foo.c:145:13: warning: 'gets' is deprecated [-Wdeprecated-declarations]
             gets(buf);
             ^~~~
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__;
              ^~~~
/tmp/ccON6xxM.o: In function `compute':
foo.c:(.text+0x128): warning: the `gets' function is dangerous and should not be used.