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

[Eli Friedman]

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.

-Eli
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