[Bug c++/11624] New: -Wnon-virtual-dtor doesn't always work

[bangerth at dealii dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11624

           Summary: -Wnon-virtual-dtor doesn't always work
           Product: gcc
           Version: 3.4
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bangerth at dealii dot org
                CC: gcc-bugs at gcc dot gnu dot org,gdr at gcc dot gnu dot
                    org

I just closed a PR that had essentially this code:
------------------------------------
struct A
{
  virtual void afunc () {};
};

struct B
{
  virtual void bfunc () {};
};

struct C : A, B
{};

int main (void)
{
  B * Bptr = new C();
  delete Bptr;
}
----------------------------
What was wrong with that PR is immaterial here, but one of the things
is that the submitter didn't recognize that he should have a virtual
destructor. That's what we have -Wnon-virtual-dtor for, I thought, since
it says:
-----------------------------------
@item -Wnon-virtual-dtor @r{(C++ only)}
@opindex Wnon-virtual-dtor
Warn when a class appears to be polymorphic, thereby requiring a virtual
destructor, yet it declares a non-virtual one.
This warning is enabled by @option{-Wall}.
-----------------------------------

Alas, this option doesn't trigger on above code, for no version after 3.2.
(I don't have an older version on my present system, so can't check.) I
think it should, though, shouldn't it?

W.