[llvm-dev] [cfe-dev] RFC: Plan for removing components from namespace std::experimental (original) (raw)

C Bergström via llvm-dev llvm-dev at lists.llvm.org
Mon Apr 10 13:29:00 PDT 2017

I think regardless of who may or may not be using experimental stuff there shouldn't be a level of guaranteed stability. As the name implies it's not stable. It's a vehicle for testing things and prototype implementations that can't make it into main. Show me another project where experimental == guaranteed stability

On Tue, Apr 11, 2017 at 4:22 AM, Marshall Clow via cfe-dev <cfe-dev at lists.llvm.org> wrote:

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::stringview * the searchers (std::experimental::boyermoore, etc) * std::experimental::randomshuffle and probably other things... Comments? -- Marshall

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