[cfe-dev] [libcxx] Removing _LIBCPP_TRIVIAL_PAIR_COPY_CTOR option.

[Eric Fiselier via cfe-dev]

Reverted in r272671.

On Tue, Jun 14, 2016 at 8:35 AM, Eric Fiselier <eric at efcs.ca> wrote:

> Thinking out loud: The Itanium spec specifies that the calling conventions
> for non-trivial types only occurs when both the copy constructor and
> destructor are trivial.
>
> I have some upcoming changes to pair that depend on the copy constructor
> being implicitly generated, which means killing those constructors.
> Perhaps we could find another way to make either the destructor or
> implicitly generated copy constructor non-trivial?
>
> I wonder if giving pair a dummy base class with a non-trivial destructor
> could serve as an alternative solution?
>
> /Eric
>
>
>
> On Tue, Jun 14, 2016 at 8:25 AM, Eric Fiselier <eric at efcs.ca> wrote:
>
>> Well that's unfortunate :-( I'll revert it later today, and we can work
>> on a solution from there.
>>
>> I would strongly encourage you to submit FreeBSD specific patches
>> upstream. It's very helpful to see who (if anybody) is using specific ABI
>> options or seemingly dead conditional compilation branches.
>>
>> /Eric
>>
>>
>>
>>
>>
>> On Tue, Jun 14, 2016 at 4:02 AM, Dimitry Andric <dimitry at andric.com>
>> wrote:
>>
>>> We still turn off, and have always turned off, the
>>> _LIBCPP_TRIVIAL_PAIR_COPY_CTOR option in FreeBSD, since we are supposed to
>>> be backwards compatible with previous versions of libc++ that we shipped;
>>> see
>>> https://svnweb.freebsd.org/base/head/contrib/libc++/include/__config?view=markup#l733
>>>
>>> If the option is completely removed, we will either have to supply two
>>> versions of libc++, or bolt on some sort of backwards compatibility
>>> versioned symbols.  Alternatively, we can add a local hack to put back the
>>> non-trivial copy constructor, but that might lead to other headaches.
>>>
>>> David, do you have any good ideas for this?  I think your idea was to
>>> burn all backwards compatibility bridges, but we can't really do that for
>>> FreeBSD 11.0 at this point, so we would have to start backporting fixes
>>> from trunk libc++, instead of importing it wholesale.  For FreeBSD 12.0 we
>>> could ship only the new libc++, and provide the older libc++ as a
>>> compatibility package.
>>>
>>> -Dimitry
>>>
>>> On 14 Jun 2016, at 03:44, Eric Fiselier via cfe-dev <
>>> cfe-dev at lists.llvm.org> wrote:
>>>
>>> I have removed this option from in the libc++ in r272613.  I believe it
>>> has no clients.
>>> If anybody uses this option please contact me.
>>>
>>> This option was used to turn off std::pair's trivial copy constructor,
>>> instead selecting an older non-trivial implementation.
>>>
>>> It was added in r194742, on November 14th 2013. At that time Apple
>>> platforms used this option to turn off pairs trivial constructor. Two weeks
>>> later, on November 26th 2013, the default value for Apple platforms was
>>> removed in r195796.
>>>
>>> Defining `_LIBCPP_TRIVIAL_PAIR_COPY_CTOR` will now cause an explicit
>>> error informing the client that the option has been removed. I will remove
>>> this diagnostic after the 3.9 release.
>>>
>>> /Eric
>>>
>>>
>>> _______________________________________________
>>> cfe-dev mailing list
>>> cfe-dev at lists.llvm.org
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>>>
>>>
>>>
>>
>
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