[Bug middle-end/58970] [4.7/4.8/4.9 Regression] internal compiler error: in get_bit_range, at expr.c:4562

[bernd.edlinger at hotmail dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58970

--- Comment #15 from Bernd Edlinger <bernd.edlinger at hotmail dot de> ---
(In reply to Bernd Edlinger from comment #14)
> (In reply to Jakub Jelinek from comment #13)
> > (In reply to Bernd Edlinger from comment #12)
> > > I meant the change here is not necessary, because after the
> > > if (*bitpos < 0) {...},
> > > *offset can no longer be NULL, and I'd leave the assertion untouched.
> > 
> > Sure, if *bitpos was initially negative, then *offset won't be NULL there.
> > But what I mean, are you sure that non-negative *bitpos will never be
> > smaller than bitoffset if *offset is NULL?  Of course not on this testcase...
> 
> If *bitpos is initially negative, I can proove that *offset is initially
> NULL.

However we can be sure (to assert), that if offset is initially NULL,
and *bitpos is initially >= 0, then
the bit offset of the bitfield representative must be >= 0 too.
because otherwiese, the bitfield would start at offset < 0 and end
at an offset > 0. Which is not possible.

Therefore bitoffset <= *bitpos if *bitpos is initially >= 0 and *offset is
initially == NULL. QED?