[PATCH] libdw: Don't crash on invalid die in dwarf_dieoffset.

[Mark Wielaard]

On Thu, May 31, 2018 at 01:02:44PM +0200, Mark Wielaard wrote:
> Add explicit test in get-units-invalid for dwarf_cuoffset and
> dwarf_dieoffset.

And that test caught another bug on 32bit systems!

>  Dwarf_Off
>  dwarf_dieoffset (Dwarf_Die *die)
>  {
> -  return (die == NULL
> +  return ((die == NULL || die->cu == NULL)
>  	  ? ~0ul
>  	  : (Dwarf_Off) (die->addr - die->cu->startp + die->cu->start));

Note that ~0ul != (Dwarf_Off) -1 on 32bit systems.
So error detection was always broken.

The reason we didn't notice before was because we had a similar bug
in eu-readelf...

I am checking in the attached patch which fixes both.
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