[PATCH] D12747: Implement [depr.c.headers]

[Richard Smith via cfe-commits]

On Tue, Oct 6, 2015 at 4:11 PM, Sean Silva <chisophugis at gmail.com> wrote:

> +extern "C++" {
> +#include <__nullptr>
> +using std::nullptr_t;
> +}
>
> Does this even compile with modules?
>

Yes. You're allowed to import a C++ module within an 'extern "C++"' block.


> On Tue, Oct 6, 2015 at 3:57 PM, Richard Smith via cfe-commits <
> cfe-commits at lists.llvm.org> wrote:
>
>> <stddef.h>. This one is tricky:
>>
>> 1) There's an (undocumented) interface between the C standard library and
>> this header, where the macros __need_ptrdiff_t, __need_size_t,
>> __need_wchar_t, __need_NULL, __need_wint_t request just a piece of this
>> header rather than the whole thing. If we see any of those, just go
>> straight to the underlying header.
>>
>> 2) We probably don't want <stddef.h> to include <cstddef> (for
>> consistency with other headers), but <stddef.h> must provide a ::nullptr_t
>> (which we don't want <cstddef> to provide). So neither header includes the
>> other. Instead, both include <__nullptr> for std::nullptr_t, and we
>> duplicate the definition of max_align_t between them, in the case where the
>> compiler's <stddef.h> doesn't provide it.
>>
>> If you prefer, I could make <stddef.h> include <cstddef> to avoid the
>> duplication of the max_align_t logic.
>>
>> This patch depends on patch 02.
>>
>> On Tue, Oct 6, 2015 at 3:42 PM, Richard Smith <richard at metafoo.co.uk>
>> wrote:
>>
>>> <setjmp.h>, an easy one. We guarantee a setjmp macro exists even if this
>>> header is somehow included from C (the C standard allows that, so it's not
>>> worth checking for __cplusplus).
>>>
>>> On Tue, Oct 6, 2015 at 3:36 PM, Richard Smith <richard at metafoo.co.uk>
>>> wrote:
>>>
>>>> Split <math.h> out of <cmath>. This is a big change, but the same
>>>> pattern as the prior ones.
>>>>
>>>> On Tue, Oct 6, 2015 at 3:28 PM, Richard Smith <richard at metafoo.co.uk>
>>>> wrote:
>>>>
>>>>> Likewise for <errno.h>, <float.h>, <inttypes.h>
>>>>>
>>>>> On Tue, Oct 6, 2015 at 3:20 PM, Richard Smith <richard at metafoo.co.uk>
>>>>> wrote:
>>>>>
>>>>>> Split <ctype.h> header out of <cctype>
>>>>>>
>>>>>> On Tue, Oct 6, 2015 at 3:07 PM, Richard Smith <richard at metafoo.co.uk>
>>>>>> wrote:
>>>>>>
>>>>>>> Next: factoring the definition of std::nullptr_t out into a separate
>>>>>>> file, so that <cstddef> and <stddef.h> can both use it, without <stddef.h>
>>>>>>> including <cstddef> and without <cstddef> providing a ::nullptr_t like
>>>>>>> <stddef.h> does.
>>>>>>>
>>>>>>> On Tue, Oct 6, 2015 at 3:02 PM, Eric Fiselier <eric at efcs.ca> wrote:
>>>>>>>
>>>>>>>> LGTM.
>>>>>>>>
>>>>>>>> On Tue, Oct 6, 2015 at 3:58 PM, Richard Smith <
>>>>>>>> richard at metafoo.co.uk> wrote:
>>>>>>>> > On Mon, Oct 5, 2015 at 7:10 PM, Eric Fiselier <eric at efcs.ca>
>>>>>>>> wrote:
>>>>>>>> >>
>>>>>>>> >> EricWF added a comment.
>>>>>>>> >>
>>>>>>>> >> I think thing change will help us close a number out outstanding
>>>>>>>> bugs. I
>>>>>>>> >> don't have any fundamental objections to this approach.  However
>>>>>>>> the size of
>>>>>>>> >> this patch scares me.  I understand the changes are mostly
>>>>>>>> mechanical but
>>>>>>>> >> their size can hide things. For example has anybody noticed that
>>>>>>>> your
>>>>>>>> >> internal changes to `<deque>` are in this patch? It would be
>>>>>>>> nice to break
>>>>>>>> >> this down into more digestible pieces that could be quickly spot
>>>>>>>> checked.
>>>>>>>> >
>>>>>>>> >
>>>>>>>> > OK. First such patch is attached. It just removes the
>>>>>>>> macro-capturing
>>>>>>>> > wrapper functions.
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
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>
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