foo.cc: In function ‘int main()’:
foo.cc:18:5: error: ‘memset’ was not declared in this scope
   18 |     memset(b,0,sizeof(b));
      |     ^~~~~~
foo.cc:3:1: note: ‘memset’ is defined in header ‘<cstring>’; did you forget to ‘#include <cstring>’?
    2 | #include <iostream>
  +++ |+#include <cstring>
    3 | using namespace std;