foo.c: In function 'main':
foo.c:22:9: warning: 'gets' is deprecated [-Wdeprecated-declarations]
   22 |         gets(a);
      |         ^~~~
In file included from foo.c:1:
/nix/store/linb70pgp53f0kygxm5wk163dx22d681-glibc-2.37-45-dev/include/stdio.h:605:14: note: declared here
  605 | extern char *gets (char *__s) __wur __attribute_deprecated__;
      |              ^~~~
foo.c:23:9: warning: 'gets' is deprecated [-Wdeprecated-declarations]
   23 |         gets(b);
      |         ^~~~
/nix/store/linb70pgp53f0kygxm5wk163dx22d681-glibc-2.37-45-dev/include/stdio.h:605:14: note: declared here
  605 | extern char *gets (char *__s) __wur __attribute_deprecated__;
      |              ^~~~
/nix/store/3r87a2wq1w4l66wnsm7rqvy608mx23h6-binutils-2.40/bin/ld: /tmp/ccOXWshm.o: in function `main':
foo.c:(.text.startup+0xb): warning: the `gets' function is dangerous and should not be used.

[Hydro](https://hydro.ac)提供评测服务