Archive for March 8th, 2012

wg21The spring 2012 meeting of ISO/IEC JTC1/SC22/WG21 (C++) was held on February 6-10 in Kona, Hawaii, USA.

Here’s the major takeaway: This is going to be a busy year as investment in C++ across the industry continues to increase, and that’s good news for C++.

Here are some highlights from the meeting.


This was the second meeting after completion of the C++11 standard. After a standard ships, often attendance will decline for a while, especially if the intent is to “go quiet” for a time to let the industry catch up, as we did after completing C++98.

As you can see below, however, it’s clear that this time the C++ committee is gearing up, not gearing down, after shipping its latest major standard. That’s reflected in record attendance: 73 experts attended, with record numbers of participants from companies like Google and Intel and Microsoft and NVidia, to avidly begin planning for work on the next standard as well as other deliverables even in advance of the next standard.

Full speed ahead, part 1: C++1y

The biggest decision we knew would be discussed was to decide “what’s next” after C++11. Right away on Monday morning we decided that WG21 will immediately begin working on a new revision of the ISO C++ standard, including both language and library extensions, with a rough target of completing work on a new “C++1y” standard in approximately five years. That is, y is hoped to be approximately 7, but that’s intended to be only a rough scope guide at this point.

To have any chance of making y be approximately 7, C++1y can add at most one major new language feature, and there are already more language extension proposals than could possibly fit. The evolution working group (EWG), chaired as usual by Bjarne Stroustrup, therefore spent much of the week surveying the landscape of major evolution proposals we might consider in this round, and we had initial presentations of several, ranging from concurrency and parallelism to modules and static if.

We tried not to make any yes/no scope decisions at this meeting, and so many of these will come up again as updated and further-refined proposals at our next full meeting in October; at that point we intend to start saying yes and no to particular proposals we want to consider for the C++1y timeframe. In the interim, some of the proposals (notably concurrency/parallelism approaches, and the module system proposals) have enough interest that subgroups will hold additional smaller face-to-face meetings this summer in between full WG21 meetings so as to make more progress in these areas; more on this below.

Full speed ahead, part 2: Libraries galore

As I reported form our last meeting, the library working group (LWG) also has already decided to immediately continue working on new extensions to the standard library, and solicited proposals. In Kona, we reaffirmed that the door is open for library extensions, and our LWG chair Alisdair Meredith issued this call for library proposals.

But these libraries aren’t just for C++1y, because the LWG intends to work on shipping new libraries in smaller pieces in order to deliver work sooner and in smaller bites. Some libraries, such as File System and Networking, are big enough and separable enough to work on as independent pieces that can even ship separately from (read: earlier than) C++1y in the form of a Technical Specification (TS). (Terminology note: TS is the new ISO term for what we used to call Type 2 Technical Reports (TR), such as the first Library Extensions TR.)

These smaller pieces will be worked on independently, and once they’re ready to bring to the full WG21 LWG it will be the LWG that decides how to progress them – as part of the C++1y International Standard (IS) or as their own standalone TS or even IS.

Study Groups

Because we’re gearing up for all this work, and so much of its parallelizable, I’ve created the first four official WG21 Study Groups (SGs) that can meet independently to progress their work between full WG21 meetings. These SGs will help to refine and progress proposals faster by working on their own, but will bring all proposals to WG21 as usual for approval and further refinement before anything is published as a TS or IS.

The first four study groups, and their chairs, are as follows:

  • SG1: Concurrency and Parallelism (Hans Boehm)
  • SG2: Modules (Doug Gregor)
  • SG3: File System (Beman Dawes)
  • SG4: Networking (Kyle Kloepper)

There will be at least one face-to-face SG meeting, and there may be more. Here’s what I know about so far:

  • Week of May 7, 2012: Bellevue, WA, USA (SG1 and SG4)
  • (if needed) Summer 2012: Toronto, Canada (SG1)

Looking forward

Besides smaller Study Group meetings, here are the planned dates and locations for upcoming meetings of the full ISO C++ standards committee:

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