Re: C++ PATCH for c++/65556 (ICE with switch and bit-fields)

[James Greenhalgh <james dot greenhalgh at arm dot com>]

On Fri, Mar 27, 2015 at 11:14:31PM +0000, H.J. Lu wrote:
> On Fri, Mar 27, 2015 at 7:38 AM, Marek Polacek <polacek@redhat.com> wrote:
> > In this testcase we were crashing while trying to gimplify a switch, because
> > the types of the switch condition and case constants didn't match.  This ICE
> > started with my -Wswitch-with-enum-bit-fields fix where I used the unlowered
> > type so that we're able to get hold of the enum type.  The problem with that
> > is with ordinary bit-fields: we'll get the underlying type (e.g. long int),
> > but subsequent perform_integral_promotions promotes that to int, see
> > cp_perform_integral_promotions.  Fixed by using the type of the condition in
> > case we're not dealing with an enum bit-field, i.e. do what we've been doing
> > before the -Wswitch fix, which ought to make this fix very safe.
> >
> > Bootstrapped/regtested on x86_64-linux, ok for trunk?
> >
> > 2015-03-27  Marek Polacek  <polacek@redhat.com>
> >
> >         PR c++/65556
> >         * semantics.c (finish_switch_cond): If the unlowered type is not an
> >         enum, use the type of the condition.
> >
> >         * c-c++-common/pr65556.c: New test.
> >
> 
> The new test is failing for me on x86-32 and x32:
> 
> https://gcc.gnu.org/ml/gcc-regression/2015-03/msg00392.html

Likewise on ARM. The testcase is fairly obviously not going to work
for any target with 32-bit long:

  struct S
  {
    long l: 1;
    long l2: 41;
    unsigned long ul: 1;
    unsigned long ul2: 41;
  } s;

  .../c-c++-common/pr65556.c:9:3: error: width of 'ul2' exceeds its type

Thanks,
James