Q1 2022 priorities

[StephanTLavavej]

In the first quarter of 2022, our priorities are:

• Implementing the C++20 Defect Reports
  • And then backporting them to VS 2019 16.11.x.
• Reviewing the PR backlog
• Implementing the C++23 features that have been accepted so far
• Writing Contribution Guidelines

We could use some help with #2475 if anyone has free time! 😸

Additionally, Miya Natsuhara (@mnatsuhara) will be looking into expanding our code review videos to add contributor-led reviews of PRs.

If you have questions about our plans for this quarter, feel free to ask them here. (Note that compiler, IDE, etc. priorities are off-topic.)

[jonwil]

Has the plan to open source vcruntime/vcstartup been dropped or is it just delayed (e.g. legal reviews, code cleanup, whatever
)

[StephanTLavavej]

Only delayed - we need to create some benchmark infrastructure before the compiler back-end team will be comfortable accepting changes to its perf-critical functions.

[jovibor]

Can you please confirm that 17.2 release will mark the C++20 ABI lockdown (due to improbable urgency the #2518 was closed),
and that we won't see any format and ranges improvements until vNext? 😭😭😎

[StephanTLavavej]

Yes, 17.2 will contain the C++20 ABI lockdown - as decided by our bosses and boss-like entities.

We can continue to improve <format> and <ranges> in ways that preserve ABI.

[AlexGuteniev]

I'm worried about #2119 and #2437 -- what would happen to them?

[StephanTLavavej]

Alex Guteniev (@AlexGuteniev) Thanks for asking! Charlie Barto (@barcharcraz) says that #2119 is definitely not ABI breaking because it doesn't change representations of data structures, and that #2437 can be made to be non-ABI-breaking by renaming internal data structures (e.g. from _Ugly to _Ugly2) so I think we should be okay there.

[jrmoore]

What is missing from <ranges>? From the blog post titled MSVC C++20 and the /std:c++20 Switch it seems P0896R4 was implemented already for VS 2019 v16.10 & v16.11, but __cpp_lib_ranges seems not to be defined.

Although it also states /std:c++20 to be ABI stable and from what I'm reading that won't happen until v17.2 😅.

[CaseyCarter]

What is missing from <ranges>? From the blog post titled MSVC C++20 and the /std:c++20 Switch it seems P0896R4 was implemented already for VS 2019 v16.10 & v16.11, but __cpp_lib_ranges seems not to be defined.

Although it also states /std:c++20 to be ABI stable and from what I'm reading that won't happen until v17.2 😅.

You can look at #1814 for full gory detail, but the short version is "We couldn't put <ranges>/<format> under /std:c++20 until WG21 stopped breaking ABI with Defect Report fixes." If you compile with /std:c++latest - the flag that explicitly asks for unstable features from in-progress implementation of the not-yet-complete next version of the C++ standard - you will see __cpp_lib_ranges is defined. But be aware that there are significant ABI-breaking changes going on until 17.2 p2 when we finally pull <ranges>/<format> into /std:c++20.

[StephanTLavavej]

Q2 2022 priorities are now pinned: #2628