virtual destructors and valgrind

Was curious to know the effects of missing a virtual destructor, and ran the program on valgrind:

Valgrind reported a memory leak.

user@ubuntu:~/devel/effective_cpp$ g++ virt_dtor.cpp -ggdb
user@ubuntu:~/devel/effective_cpp$ cat virt_dtor.cpp 
#include 
using namespace std;

class Base{
    public:
    ~Base() { cout << "~Base()" << endl; }
};

class Der: public Base{
    public:
        int* array;
     Der(){ array = new int[10]; }
    ~Der() { cout << "~Der()" << endl; delete[] array; }
};

int main()
{
    Base* b  = new Der;
    delete b;
}
user@ubuntu:~/devel/effective_cpp$ valgrind --leak-check=full ./a.out 
==2791== Memcheck, a memory error detector
==2791== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al.
==2791== Using Valgrind-3.6.0.SVN-Debian and LibVEX; rerun with -h for copyright info
==2791== Command: ./a.out
==2791== 
~Base()
==2791== 
==2791== HEAP SUMMARY:
==2791==     in use at exit: 40 bytes in 1 blocks
==2791==   total heap usage: 2 allocs, 1 frees, 44 bytes allocated
==2791== 
==2791== 40 bytes in 1 blocks are definitely lost in loss record 1 of 1
==2791==    at 0x4025FE5: operator new[](unsigned int) (vg_replace_malloc.c:299)
==2791==    by 0x80488C8: Der::Der() (virt_dtor.cpp:12)
==2791==    by 0x80487A7: main (virt_dtor.cpp:18)
==2791== 
==2791== LEAK SUMMARY:
==2791==    definitely lost: 40 bytes in 1 blocks
==2791==    indirectly lost: 0 bytes in 0 blocks
==2791==      possibly lost: 0 bytes in 0 blocks
==2791==    still reachable: 0 bytes in 0 blocks
==2791==         suppressed: 0 bytes in 0 blocks
==2791== 
==2791== For counts of detected and suppressed errors, rerun with: -v
==2791== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 19 from 8)