foo.c: In function 'main':
foo.c:5:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
    5 |  gets(s1);
      |  ^~~~
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:6:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
    6 |  gets(s2);
      |  ^~~~
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:7:5: warning: implicit declaration of function 'strlen' [-Wimplicit-function-declaration]
    7 |  s1[strlen(s1)-1]=0;
      |     ^~~~~~
foo.c:7:5: warning: incompatible implicit declaration of built-in function 'strlen'
foo.c:2:1: note: include '<string.h>' or provide a declaration of 'strlen'
    1 | #include<stdio.h>
  +++ |+#include <string.h>
    2 | int main()
foo.c:8:2: warning: implicit declaration of function 'strcat' [-Wimplicit-function-declaration]
    8 |  strcat(s1,s2+1);
      |  ^~~~~~
foo.c:8:2: warning: incompatible implicit declaration of built-in function 'strcat'
foo.c:8:2: note: include '<string.h>' or provide a declaration of 'strcat'
foo.c:5:2: warning: ignoring return value of 'gets', declared with attribute warn_unused_result [-Wunused-result]
    5 |  gets(s1);
      |  ^~~~~~~~
foo.c:6:2: warning: ignoring return value of 'gets', declared with attribute warn_unused_result [-Wunused-result]
    6 |  gets(s2);
      |  ^~~~~~~~
/usr/bin/ld: /tmp/ccKOO9I9.o: in function `main':
foo.c:(.text.startup+0x45): warning: the `gets' function is dangerous and should not be used.

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