[libcxx] r227226 - [libcxx] Make __wrap_iter work with gcc.

[David Blaikie]

On Tue, Jan 27, 2015 at 3:24 PM, Nico Weber <thakis at chromium.org> wrote:

> On Tue, Jan 27, 2015 at 3:19 PM, David Blaikie <dblaikie at gmail.com> wrote:
>
>>
>>
>> On Tue, Jan 27, 2015 at 11:27 AM, Nico Weber <nicolasweber at gmx.de> wrote:
>>
>>> Author: nico
>>> Date: Tue Jan 27 13:27:39 2015
>>> New Revision: 227226
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=227226&view=rev
>>> Log:
>>> [libcxx] Make __wrap_iter work with gcc.
>>>
>>> he following snippet doesn't build when using gcc and libc++:
>>>
>>>     #include <string>
>>>     void f(const std::string& s) { s.begin(); }
>>>     #include <vector>
>>>     void AppendTo(const std::vector<char>& v) { v.begin(); }
>>>
>>> The problem is that __wrap_iter has a private constructor. It lists
>>> vector<>
>>> and basic_string<> as friends, but gcc seems to ignore this for vector<>
>>> for
>>> some reason. Declaring vector before the friend declaration in
>>> __wrap_iter is
>>> enough to work around this problem, so do that. With this patch, I'm
>>> able to
>>> build chromium/android with libc++. Without it, two translation units
>>> fail to
>>> build. (iosfwd already provides a forward declaration of basic_string.)
>>>
>>> As far as I can tell, this is due to a gcc bug, which I filed as
>>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64816.
>>>
>>> Fixes PR22355.
>>>
>>> http://reviews.llvm.org/D7201
>>>
>>> Added:
>>>
>>> libcxx/trunk/test/std/iterators/iterators.general/gcc_workaround.pass.cpp
>>> Modified:
>>>     libcxx/trunk/include/iterator
>>>
>>> Modified: libcxx/trunk/include/iterator
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/iterator?rev=227226&r1=227225&r2=227226&view=diff
>>>
>>> ==============================================================================
>>> --- libcxx/trunk/include/iterator (original)
>>> +++ libcxx/trunk/include/iterator Tue Jan 27 13:27:39 2015
>>> @@ -1112,6 +1112,8 @@ typename enable_if
>>>  >::type
>>>  __unwrap_iter(__wrap_iter<_Tp*>);
>>>
>>> +template <class _Tp, class _Alloc> class _LIBCPP_TYPE_VIS_ONLY vector;
>>>
>>
>> Worth including a comment that this is a workaround for a particular bug
>>
>
> I went with the prevalent documentation style in libc++ :-)
>

;) revision history will hopefully suffice.


>
>
>> (is there a GCC bug filed for this?)?
>>
>
> Yes, see this snippet in the CL description:
>
> """
> As far as I can tell, this is due to a gcc bug, which I filed as
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64816.
> """
>
> There's some more rambling on the topic (a link to a clang bug I found
> while working on this, etc) in the mentioned PR22355 too.
>

Ah, right - sorry I missed that.


>
>
>>
>>
>>> +
>>>  template <class _Iter>
>>>  class __wrap_iter
>>>  {
>>>
>>> Added:
>>> libcxx/trunk/test/std/iterators/iterators.general/gcc_workaround.pass.cpp
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/libcxx/trunk/test/std/iterators/iterators.general/gcc_workaround.pass.cpp?rev=227226&view=auto
>>>
>>> ==============================================================================
>>> ---
>>> libcxx/trunk/test/std/iterators/iterators.general/gcc_workaround.pass.cpp
>>> (added)
>>> +++
>>> libcxx/trunk/test/std/iterators/iterators.general/gcc_workaround.pass.cpp
>>> Tue Jan 27 13:27:39 2015
>>> @@ -0,0 +1,20 @@
>>>
>>> +//===----------------------------------------------------------------------===//
>>> +//
>>> +//                     The LLVM Compiler Infrastructure
>>> +//
>>> +// This file is dual licensed under the MIT and the University of
>>> Illinois Open
>>> +// Source Licenses. See LICENSE.TXT for details.
>>> +//
>>>
>>> +//===----------------------------------------------------------------------===//
>>> +
>>> +// Tests workaround for
>>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64816.
>>> +
>>> +#include <string>
>>> +
>>> +void f(const std::string &s) { s.begin(); }
>>> +
>>> +#include <vector>
>>> +
>>> +void AppendTo(const std::vector<char> &v) { v.begin(); }
>>> +
>>> +int main() {}
>>>
>>>
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>>>
>>
>>
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