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

[Nico Weber]

Looking…


On Thu, Jun 20, 2013 at 3:19 PM, Eli Friedman <eli.friedman at gmail.com>wrote:

> On Thu, Jun 20, 2013 at 3:10 PM, Eli Friedman <eli.friedman at gmail.com>wrote:
>
>> 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.
>>
>
>
> Just checked; the following crashes with your patch:
>
> void f(int x, __float128*y) { x+*y; }
>
> =Eli
>
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