foo.c: In function 'main':
foo.c:17:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(s1);gets(s2);
  ^~~~
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:17:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(s1);gets(s2);
  ^~~~
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:16:36: warning: unused variable 'l4' [-Wunused-variable]
  char s1[10000],l1,l3,s2[10000],l2,l4;
                                    ^~
foo.c:16:20: warning: unused variable 'l3' [-Wunused-variable]
  char s1[10000],l1,l3,s2[10000],l2,l4;
                    ^~
/tmp/ccZRUYWX.o: In function `main':
foo.c:(.text.startup+0x15): 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)