foo.c: In function 'main':
foo.c:9:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
    9 |  gets(a1);
      |  ^~~~
In file included from /usr/include/stdio.h:867,
                 from foo.c:1:
/usr/include/x86_64-linux-gnu/bits/stdio2.h:235:1: note: declared here
  235 | gets (char *__str)
      | ^~~~
foo.c:10:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
   10 |  gets(a2);
      |  ^~~~
In file included from /usr/include/stdio.h:867,
                 from foo.c:1:
/usr/include/x86_64-linux-gnu/bits/stdio2.h:235:1: note: declared here
  235 | gets (char *__str)
      | ^~~~
foo.c:9:2: warning: ignoring return value of 'gets', declared with attribute warn_unused_result [-Wunused-result]
    9 |  gets(a1);
      |  ^~~~~~~~
foo.c:10:2: warning: ignoring return value of 'gets', declared with attribute warn_unused_result [-Wunused-result]
   10 |  gets(a2);
      |  ^~~~~~~~
In file included from /usr/include/string.h:495,
                 from foo.c:2:
In function 'strncpy',
    inlined from 'main' at foo.c:11:2:
/usr/include/x86_64-linux-gnu/bits/string_fortified.h:106:10: warning: '__builtin___strncpy_chk' specified bound depends on the length of the source argument [-Wstringop-overflow=]
  106 |   return __builtin___strncpy_chk (__dest, __src, __len, __bos (__dest));
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.c: In function 'main':
foo.c:11:18: note: length computed here
   11 |  strncpy(a3, a1, strlen(a1)-1);
      |                  ^~~~~~~~~~
/usr/bin/ld: /tmp/ccVsOAdG.o: in function `main':
foo.c:(.text.startup+0x15): warning: the `gets' function is dangerous and should not be used.

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