[cfe-dev] Crash on conditional operation with address_space pointer

[Leonard Chan via cfe-dev]

Added you to https://reviews.llvm.org/D50278
On Fri, Aug 3, 2018 at 5:27 PM John McCall <rjmccall at apple.com> wrote:
>
> > On Aug 3, 2018, at 8:05 PM, Leonard Chan <leonardchan at google.com> wrote:
> > Oh I see. I misinterpreted a few things. I'll change the patch to
> > print something from err_typecheck_incompatible_address_space instead
> > in addition to raising the warning.
>
> Great, please CC me on the review when you put it up.
>
> John.
>
> > On Fri, Aug 3, 2018 at 4:57 PM John McCall <rjmccall at apple.com> wrote:
> >>
> >>> On Aug 3, 2018, at 7:56 PM, Leonard Chan <leonardchan at google.com> wrote:
> >>> Oh. Should an error be printed here instead, or it's fine to let it
> >>> crash I suppose since the code shouldn't be generate in the first
> >>> place?
> >>>
> >>> It seems that at least 3 tests expect this conditional operator to
> >>> print a "pointer type mismatch" warning.
> >>
> >> The compiler should definitely never crash.  That sounds like the right diagnostic
> >> we should be emitting, except I don't think it can be just a warning for an
> >> address-space mismatch.
> >>
> >> John.
> >>
> >>> On Fri, Aug 3, 2018 at 4:50 PM John McCall <rjmccall at apple.com> wrote:
> >>>>
> >>>>> On Aug 3, 2018, at 7:42 PM, Leonard Chan <leonardchan at google.com> wrote:
> >>>>> Does this mean the check during the BitCast codegen shouldn't be there
> >>>>> in the first place?
> >>>>
> >>>> We should not be generating code for this program, correct.
> >>>>
> >>>> John.
> >>>>
> >>>>> On Fri, Aug 3, 2018 at 4:28 PM John McCall <rjmccall at apple.com> wrote:
> >>>>>>
> >>>>>>> On Aug 3, 2018, at 7:03 PM, Leonard Chan via cfe-dev <cfe-dev at lists.llvm.org> wrote:
> >>>>>>> Compiling the following causes clang to crash
> >>>>>>>
> >>>>>>> char *cmp(__attribute__((address_space(1))) char *x,
> >>>>>>> __attribute__((address_space(2))) char *y) {
> >>>>>>> return x < y ? x : y;
> >>>>>>> }
> >>>>>>>
> >>>>>>> with the message: "wrong cast for pointers in different address
> >>>>>>> spaces(must be an address space cast)!"
> >>>>>>>
> >>>>>>> The problem seems to be that BitCast is used when
> >>>>>>> AddressSpaceConversion should be used instead when casting the `y` to
> >>>>>>> a void *. The error is thrown during code gen where a BitCast expects
> >>>>>>> the source and dest address space to be the same.
> >>>>>>>
> >>>>>>> I submitted a patch (https://reviews.llvm.org/D50278) for a fix where
> >>>>>>> we check for differing address spaces in the operands and perform an
> >>>>>>> AddressSpaceConversion cast if anyone wants to review it. It seems
> >>>>>>> that AddressSpaceConversions though were only available when using
> >>>>>>> OpenCL. I'm not familiar with OpenCL and not sure if this was
> >>>>>>> intended, but it fixes the crash while still retaining the warning of
> >>>>>>> using mismatched pointers and all the clang tests pass.
> >>>>>>
> >>>>>> If address spaces 1 and 2 don't overlap — and absent target-specific
> >>>>>> information, the assumption is that they don't — then neither the comparison
> >>>>>> nor the conditional operator here should type-check.
> >>>>>>
> >>>>>> John.
> >>>>
> >>
>