Re: [Qemu-devel] [PATCH for-3.1? 2/3] migration: fix stringop-truncation warning

["Marc-André Lureau" <marcandre.lureau@redhat.com>]

Hi

On Tue, Nov 20, 2018 at 9:22 PM Dr. David Alan Gilbert
<dgilbert@redhat.com> wrote:
>
> * Eric Blake (eblake@redhat.com) wrote:
> > On 11/20/18 9:27 AM, Marc-André Lureau wrote:
> > > Adding an assert is enough to silence GCC.
> > >
> > > ~/src/qemu/migration/global_state.c: In function 'global_state_store_running':
> > > ~/src/qemu/migration/global_state.c:45:5: error: 'strncpy' specified bound 100 equals destination size [-Werror=stringop-truncation]
> > >       strncpy((char *)global_state.runstate,
> > >       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > >              state, sizeof(global_state.runstate));
> > >              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > cc1: all warnings being treated as errors
> > >
> > > (alternatively, we could hard-code "running")
> > >
> > > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> > > ---
> > >   migration/global_state.c | 1 +
> > >   1 file changed, 1 insertion(+)
> >
> > Reviewed-by: Eric Blake <eblake@redhat.com>
> >
> > I think this is safe for 3.1, but I know the migration code is particularly
> > wary of assert()s, even when they are non-triggerable (a 100-byte buffer at
> > global_state.runstate is big enough for ALL of the run states, not just
> > RUN_STATE_RUNNING).
>
> That's OK; the universe would have to be particularly broken to trigger
> that one, and it's in no way connected with any state, so it would
> trigger on even the most basic tests.
>
> However, I wonder if this fixes the problem on mingw builds - windows
> asserts are not marked as noreturn.

On f29, with mingw64-gcc-8.2.0-3.fc29.x86_64, it fixes the warning.

>
> Dave
>
> > >
> > > diff --git a/migration/global_state.c b/migration/global_state.c
> > > index 8e8ab5c51e..01805c567a 100644
> > > --- a/migration/global_state.c
> > > +++ b/migration/global_state.c
> > > @@ -42,6 +42,7 @@ int global_state_store(void)
> > >   void global_state_store_running(void)
> > >   {
> > >       const char *state = RunState_str(RUN_STATE_RUNNING);
> > > +    assert(strlen(state) < sizeof(global_state.runstate));
> > >       strncpy((char *)global_state.runstate,
> > >              state, sizeof(global_state.runstate));
> > >   }
> > >
> >
> > --
> > Eric Blake, Principal Software Engineer
> > Red Hat, Inc.           +1-919-301-3266
> > Virtualization:  qemu.org | libvirt.org
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK