foo.c: In function 'main':
foo.c:12:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(string1);
  ^~~~
In file included from foo.c:1:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
foo.c:13:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(string2);
  ^~~~
In file included from foo.c:1:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
foo.c:11:33: warning: unused variable 'len2' [-Wunused-variable]
  int up_count, low_count, len1, len2;
                                 ^~~~
foo.c:11:27: warning: unused variable 'len1' [-Wunused-variable]
  int up_count, low_count, len1, len2;
                           ^~~~
foo.c:11:16: warning: unused variable 'low_count' [-Wunused-variable]
  int up_count, low_count, len1, len2;
                ^~~~~~~~~
foo.c:11:6: warning: unused variable 'up_count' [-Wunused-variable]
  int up_count, low_count, len1, len2;
      ^~~~~~~~
/tmp/ccTkKu5v.o: In function `main':
foo.c:(.text.startup+0x18): warning: the `gets' function is dangerous and should not be used.

自豪的采用jd5进行评测(github.com/masnn/jd5)