[llvm-dev] RFC: Plan for removing components from namespace std::experimental

Marshall Clow via llvm-dev llvm-dev at lists.llvm.org
Wed Jan 3 16:43:38 PST 2018

On Mon, Apr 10, 2017 at 1:22 PM, Marshall Clow <mclow.lists at gmail.com>

> As part of the work on C++17, WG21 released a series of "Technical
> Specifications", (TS) which added proposed new features to the standard
> library. These were all defined in the namespace 'std::experimental' (and
> namespaces inside of that).
> Then, much of these features were merged into the main standard, and
> became part of namespace 'std'.  Libc++ now has two implementations of
> several of these, and they are diverging (because changes were made to the
> ones in the main standard, but not to the ones in the TS.
> In the long run, I would like to remove the TS versions of these features
> from libc++ - since there are "better" versions in the main standard now.
> However, since people are using these, I don't think yanking them w/o
> warning is the right thing to do.
> So, I'm proposing a new policy, and a timetable:
> One year.
> One year after we ship a LLVM release that supports a new C++ standard, we
> will remove all the features that are in the 'experimental' namespace that
> are implemented in the new standard).
> Applying this policy to C++17,  we get:
> LLVM 5.0 will support C++17.
> So, for LLVM 7.0, we will remove (at least) the following features from
> libc++
> * std::experimental::filesystem
> * std::experimental::optional
> * std::experimental::any
> * std::experimental::string_view
> * the searchers (std::experimental::boyer_moore, etc)
> * std::experimental::random_shuffle
> and probably other things...
Now that we have branched for 6.0, we can do this. ;-)
I'll be rolling out details this week ....

-- Marshall
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