https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106080
--- Comment #10 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #8)
> (In reply to Marek Polacek from comment #7)
> > I know you can't jump into a statement expression but that's not what's
> > happening here. The kernel uses this trick to get the current address for
> > error messages:
> >
> > #define __this_address ({ __label__ __here; __here: barrier(); &&__here; })
> >
> > and they will have to disable the warning completely because of it. The
> > manual for -Wdangling-pointer also talks about pointers to *objects* and
> > labels aren't objects.
>
> But that is undefined at what label or even where label would be located; it
> could be located anywhere. The kernel use of this extension should be
> removed as it is not using it to get an useful value at all. Maybe we should
> add another builtin to get the current PC.
Apparently it's worked for them. XFS uses __this_address as defined above, the
rest of the kernel uses
#define _RET_IP_ (unsigned long)__builtin_return_address(0)
#define _THIS_IP_ ({ __label__ __here; __here: (unsigned long)&&__here; })
Maybe we should have __builtin_current_pc but we don't.
> Also can't they turn off the warning inside the statement expression/around
> the macro?
That's a question for them. I continue to think that warning about non-objects
is a flaw and not useful.
