[patch] Let stddef.h redefine NULL if __need_NULL is set

[Reid Kleckner]

On Mon, Apr 28, 2014 at 1:16 PM, Nico Weber <thakis at chromium.org> wrote:

> On Mon, Apr 28, 2014 at 1:05 PM, Reid Kleckner <rnk at google.com> wrote:
>
>> Even if we commit this workaround, can we report this as a bug to
>> upstream Linux?
>>
>
> As mentioned above, I'm guessing Linux probably doesn't want to depend on
> C standard headers, so they wouldn't see this as a bug in Linux.
>
> You could say that it's a bug in glibc that they include headers that pull
> in Linux's internal linux/stddef.h in glibc headers used by applications,
> but based on previous interactions with glibc I would guess that their
> reply would be "we do include this internal linux header, but we're careful
> to define __need_NULL and re-include stddef.h to fix the issues caused by
> that". (I'm happy to file a bug like this if you think it has a chance of
> not being WontFixed immediately.)
>

I don't think they'll be responsive.


>  The test case you have shows how this definition of NULL is broken on
>> x86_64, even in C with gcc:
>>
>
> The Linux header does
>
> #if c++
> #define NULL 0
> #else
> #define NULL (void*)0
> #endif
>
> so that should be fine (?)
>

Great, so they have a definition that follows the letter of the C++
standard, but not the intention.  I doubt they will change their headers to
be more C++-friendly.  IIRC they were famous for using C++ keywords in
headers in the past.

Let's commit the workaround.  It's what glibc wants.
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