On Sun, Aug 4, 2019 at 6:16 AM Sam Varshavchik <mrsam@xxxxxxxxxxxxxxx> wrote:
>
> Georg Sauthoff writes:
>
> > > I ended up tweaking my code to avoid the assertions, rather than disabling
> > > them. For this particular situation, my original change was to try
> > >
> > > std::copy(&foo[0], &foo[0]+foo.size(), std::back_insert_iterator{bar});
> > >
> > > But that still tripped the assertion when the foo vector was empty, so I
> > had
> > > wrap this inside an if().
> >
> > But why don't you use the idiomatic
> >
> > copy(foo.begin(), foo.end(), back_inserter(bar));
> >
> > ?
> >
> > No need to wrap it into an extra if statement.
>
> I'm well aware of the alternatives. That's not the point.
>
> The point is that there's nothing wrong with this specific form of existing
> code that now throws exceptions when the hardened build gets turned on.
> There is no buffer overruns, and nothing to exploit.
>
> IIRC, the hardened build did find one real bug in the upstream package that
> was the original subject matter here, but all of the rest were these kinds
> of false positives. Now you have a situation when the existing code is known
> to be working, but needs changing in order to use a hardened build. There's
> some level of risk of regression in any change, and that gets weighed
> against the benefits of having a hardened build.
>
> The above was just a basic example of this. It is not true that exceptions
> from hardened code are always evidence of potentially exploitable problem.
> Sometimes/most of the time, but sometimes they are false positives.
>
>
I filed an upstream bug:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91357
Depending on the resolution of that bug, I suggest that Fedora
consider dropping _GLIBCXX_ASSERTIONS from the default hardened build
options. IMO Fedora's default RPM build options should not cause
crashes on valid, if less-than-stylistically-great, code. I don't
think that package maintainers should need to update package source to
use C++ in a more polite way.
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