/in/foo.c:3:6: warning: return type of 'main' is not 'int' [-Wmain]
 void main()
      ^~~~
/in/foo.c: In function 'main':
/in/foo.c:6:8: warning: multi-character character constant [-Wmultichar]
  scanf('%d',&a);
        ^~~~
/in/foo.c:6:8: warning: passing argument 1 of 'scanf' makes pointer from integer without a cast [-Wint-conversion]
In file included from /usr/include/features.h:364:0,
                 from /usr/include/stdio.h:27,
                 from /in/foo.c:1:
/usr/include/stdio.h:448:12: note: expected 'const char * restrict' but argument is of type 'int'
 extern int __REDIRECT (scanf, (const char *__restrict __format, ...),
            ^
/in/foo.c:7:8: warning: multi-character character constant [-Wmultichar]
  scanf('%d',&b);
        ^~~~
/in/foo.c:7:8: warning: passing argument 1 of 'scanf' makes pointer from integer without a cast [-Wint-conversion]
In file included from /usr/include/features.h:364:0,
                 from /usr/include/stdio.h:27,
                 from /in/foo.c:1:
/usr/include/stdio.h:448:12: note: expected 'const char * restrict' but argument is of type 'int'
 extern int __REDIRECT (scanf, (const char *__restrict __format, ...),
            ^
/in/foo.c:8:9: warning: multi-character character constant [-Wmultichar]
  printf('%d\n',a+b);
         ^~~~~~
/in/foo.c:8:9: warning: passing argument 1 of 'printf' makes pointer from integer without a cast [-Wint-conversion]
In file included from /in/foo.c:1:0:
/usr/include/stdio.h:364:12: note: expected 'const char * restrict' but argument is of type 'int'
 extern int printf (const char *__restrict __format, ...);
            ^~~~~~