[forwarded from http://bugs.debian.org/212260]

This code:

#include <stdio.h>
struct foo {
        ~foo() { }
        virtual void bar() { }
};

struct fum: public foo {
        virtual ~fum() { printf("x\n"); }
};
main() { foo *x = new fum; delete x; }

generates:

blah.cc:2: warning: `struct foo' has virtual functions but non-virtual
destructor

and "x" is not output.  (This is expected.)

Comment out the ~foo dtor.  The code is still incorrect ("x" is still
not output), but no warning is reported.  As the default dtor is
non-virtual, this warning should also be output if an object has virtual
functions but no destructor at all.