[patch] Lazily provide a __float128 type in -std=gnu++11 mode

[Eli Friedman]

On Thu, Jun 20, 2013 at 2:46 PM, Nico Weber <thakis at chromium.org> wrote:

> On Thu, Jun 20, 2013 at 2:29 PM, Eli Friedman <eli.friedman at gmail.com>wrote:
>
>> On Thu, Jun 20, 2013 at 2:25 PM, Nico Weber <thakis at chromium.org> wrote:
>>
>>> Thanks for the quick review!
>>>
>>> On Thu, Jun 20, 2013 at 2:02 PM, Eli Friedman <eli.friedman at gmail.com>wrote:
>>>
>>>>  On Thu, Jun 20, 2013 at 1:45 PM, Nico Weber <thakis at chromium.org>wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> the attached patch lazily inserts a __float128 type the first time one
>>>>> is looked up. This is needed to compile libstdc++4.7+ headers in
>>>>> -std=gnu++11 mode. This fixes PR13530, see that bug for more information.
>>>>>
>>>>> Ok?
>>>>>
>>>>
>>>> Is there any particular reason you're checking for GNUMode?
>>>>
>>>
>>> Yes, type_traits only adds __is_floating_pointer_helper<__float128> if
>>> __STRICT_ANSI__ isn't defined. InitPreprocessor.cpp defines this exactly if
>>> !GNUMode. I changed the test to check for __STRICT_ANSI__ to maybe make
>>> this a bit clearer.
>>>
>>>
>>>> "variable has incomplete type '__float128'" is a terrible error message
>>>> if someone actually tries to use __float128 with clang.  Can we do better?
>>>>
>>>
>>> We can, attached.
>>>
>>>
>>>
>> Not sure if this catches all cases, but it's probably good enough.
>>
>> Otherwise, looks fine.
>>
>
> r184476, thanks!
>
> I looked through a few diags in DiagnosticSemaKind mentioning "incomplete
> type", and the ones I checked all go through RequireCompleteType (I checked
> err_incomplete_type err_typecheck_decl_incomplete_type
> err_invalid_incomplete_type_use err_bad_dynamic_cast_incomplete
> err_incomplete_typeid err_new_incomplete_type warn_delete_incomplete
> err_catch_incomplete_ptr err_catch_incomplete_ref err_throw_incomplete
> err_throw_incomplete_ptr err_incomplete_object_call)
>
>
>
We pretty consistently go through RequireCompleteType, yes.  I was more
worried about something like "x + *y", where y is a __float128*; I don't
think we actually use RequireCompleteType to produce a diagnostic in that
case.

-Eli
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