An unsigned int value that does not produce the correct result

Question

the following program should print “error,” but printing it successfully .why?

#include<iostream>
using namespace std;
int main()
{ 
   unsigned int a;
   a=-10;

   if(a == -10)
        cout << "success" ;
   else
        cout << "error" ;

   return 0;
}

Answer 1

The conversion for comparison makes them equal again. But this should make the compiler issue a warning.