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

[Eric Fiselier via cfe-dev]

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
>
>
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