foo.cc: In function 'int main()':
foo.cc:10:5: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
     gets(s1); gets(s2);
     ^~~~
In file included from /usr/include/c++/6/cstdio:42:0,
                 from foo.cc:1:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
foo.cc:10:12: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
     gets(s1); gets(s2);
            ^
In file included from /usr/include/c++/6/cstdio:42:0,
                 from foo.cc:1:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
foo.cc:10:15: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
     gets(s1); gets(s2);
               ^~~~
In file included from /usr/include/c++/6/cstdio:42:0,
                 from foo.cc:1:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
foo.cc:10:22: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
     gets(s1); gets(s2);
                      ^
In file included from /usr/include/c++/6/cstdio:42:0,
                 from foo.cc:1:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
foo.cc:11:41: warning: unused variable 'x' [-Wunused-variable]
     int i,j,l1=strlen(s1),l2=strlen(s2),x=0;
                                         ^
/tmp/ccMSCKdF.o: In function `main':
foo.cc:(.text.startup+0xc): 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)