New paper: N3631, C11: The New C Standard -- Tom Plum

By Blog Staff | Apr 9, 2013 03:44 PM | Tags: None

Note: Both this paper by Tom Plum and the other just posted by Bjarne Stroustrup refer to prior published articles about C and C++ compatibility. The reason for drawing attention to that information is that C and C++ compatibility is now expected to be discussed at next week's ISO C++ meeting in Bristol. For an example why this discussion is taking place now, see paper N3557 section 7, which raises the question of compatibility between C and C++ for parallelism, including that pressure from C choices affects our design choices for C++ as well.

However, the C++ committee's focus at Bristol is still on working toward a Committee Draft ballot for C++14. This C/C++ compatibility discussion is expected to take place late in the meeting when the technical work for C++ in general and C++14 in particular is complete.

A new WG21 paper is available. A copy is linked below, and the paper will also appear in the next normal WG21 mailing. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N3631

Date: 2013-04-09

C11: The New C Standard

by Tom Plum

Excerpt, including explaining why the above title is not a link:

This material was originally published in a series of articles in Dr. Dobb’s (www.drdobbs.com) and is reprinted here, with permission, for use by C++ committee members. Outside the committee, please refer to readers to the following links, rather than distributing this document. (Copyright 2012 Dr. Dobb’s)

http://www.drdobbs.com/cpp/232800444 (C11 overview, concurrency, etc.)

http://www.drdobbs.com/cpp/232901670 (C11 security, Annex K, Annex L)

http://www.drdobbs.com/cpp/240001401 (Alignment, Unicode, ease‐of‐use features, C++ compatibility)

New paper: N3628, C and C++ Compatibility -- Bjarne Stroustrup

By Blog Staff | Apr 9, 2013 11:49 AM | Tags: None

A new WG21 paper is available. A copy is linked below, and the paper will also appear in the next normal WG21 mailing. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N3628

Date: 2013-04-08

C and C++ Compatibility

by Bjarne Stroustrup

Excerpt:

It seems that a serious discussion about C/C++ compatibility is starting. “By popular demand,” here is a paper in three parts that I wrote just over 10 years ago. Much have changed since that, so please don’t expect the paper to be completely up-to-date or to completely reflect my current views. However, I don’t have the time to write a 2013 version of these 2002 papers, and I don’t change my fundamental opinions all that often. I think that C/C++ compatibility is very important and valuable for both the C and C++ communities.

• C and C++: Siblings. The C/C++ Users Journal. July 2002.
• C and C++: A Case for Compatibility. The C/C++ Users Journal. August 2002.
• C and C++: Case Studies in Compatibility. The C/C++ Users Journal. September 2002.

A Look at C++14 and Beyond: Papers Part 3 -- Meeting C++

By Blog Staff | Apr 3, 2013 05:35 PM | Tags: None

And part 3:

A look at C++14 and beyond: Papers Part 3

This is the 3rd part of my little series over the papers in the Pre-Bristol mailing. I have added "and beyond" to the title, as I decided to handle all papers with Part 2, and now will continue to do so. This edition will again feature a few highlights, and a lot of proposals from different areas of C++.

Also, please understand, that all of the papers here are proposals. None of them are voted into any standard yet, maybe Bristol will give us a hint about what to expect for C++14, maybe not. Still, the proposals will give an impression, on what C++14 could be like.

A Look at C++14: Papers Part 2 -- Meeting C++

By Blog Staff | Apr 2, 2013 02:28 AM | Tags: None

A few days ago, we linked to Part 1. As noted there, although the article is labeled “A look at C++14,” not all of these papers are for C++14, and regardless of timeframe not all will be adopted. But it is a useful look at what’s on the commitee’s radar.

Part 2 has just been posted:

A look at C++14: Papers Part 2

This is the second part of my C++ Standardization Papers series. The first part has been received quite well, with more then 5k views in the first two days. Also isocpp.org, Phoronix, lwn.net, a lot of russian blogs and others have linked to it. There also was a nice discussion on reddit. Again, like in Part 1, I want to emphasize, that I only cover part of all papers in this blog post. Also not all of these papers are meant to be happening with C++14, modules & concepts for example are not going to be part of C++14 (at least this is highly unlikely). Still, I will cover those papers too, as some of them will be discussed in Bristol for sure. All papers can be found here.

Some words on C++14. C++14 is not going to be like C++11 changing the language a lot. Its more meant to enhance the language with libraries, and improve or provide bug fixes for C++11. That's why you could call C++14 a minor Standard, and the next major C++ Standard is C++17, at least you could see this as the current plan and road map for C++. But lets have a look at the papers: ...

A Look at C++14: Papers Part I -- Meeting C++

By Blog Staff | Mar 28, 2013 04:18 PM | Tags: None

[Ed. Note: Although labeled "A look at C++14," not all of these papers are for C++14, and regardless of timeframe not all will be adopted. But it is a useful look at what's on the commitee's radar.]

As we gear up for the Bristol meeting that starts on April 15, the committee members now are busily reading and preparing positions on the many papers to be considered at the meeting.

Since our last meeting in Portland, we have a recent-record-level 160 technical papers, most of which are proposals that will need to be considered and discussed at the face-to-face meeting.

Those papers have been posted here; see the blog's Standardization category. Most recently, the papers have been posted individually with crafted excerpts, and many committee members have found that useful and already follow the mailings primarily here on the blog like everyone else.

However, it's not just the committee members who are interested in these proposals. The Meeting C++ blog has posted the first of a multi-part series of "digest" summaries of the papers in the March mailing (they skipped the January mailing). In this first installment, they summarize a first batch of papers...

A look at C++14: Papers Part I

This is the first Part of n, or lets say many entries in this blog. In total I hope to be able to cover most papers in 3-4 blog posts, giving the reader an overview over the suggestions and changes for C++ at the coming C++ Committee Meeting in April. In total there are 98 Papers, so I will skip some, but try to get as much covered as possible. I'll skip papers with Meeting Minutes for sure, and try to focus on those focusing on C++11 or C++14 features. As the papers are ordered by there Number (N3522 being the first), I'll go top down, so every blog post will contain different papers from different fields of C++ Standardization. As N352-24 are Reports about Active Issues, Defects and Closed Issues I'll skip them for now, also I will not read through Meeting Minutes and such.

Quick Q: So what's "lite" about "concepts lite" vs. full concepts?

By Blog Staff | Mar 28, 2013 03:47 PM | Tags: experimental

There's a Q&A on StackOverflow, but see also the discussion about this in the March 12 Concepts conference call minutes that were posted here on the same day as the call. It's really more than minutes, it's also a record of discussion that answers this and other questions.

From SO:

What are the differences between concepts and template constraints?

I want to know what are the semantic differences between the C++ full concepts proposal and template constraints (for instance, constraints as appeared in Dlang or the new concepts-lite proposal for C++1y).

What are full-fledged concepts capable of doing than template constraints cannot do?

Pre-Bristol standards papers mailing available

By Blog Staff | Mar 19, 2013 12:13 PM | Tags: None

The official pre-meeting standards papers mailing is now available. It includes the spring meeting agenda, updated issues lists, and a number of new papers including at least one that came through the public std-proposals forum. (Update: Please also direct discussion about these papers to that forum.)

Note: Most or all of these papers have also been posted already to this site's Standardization RSS feed.

New paper: N3620, Network Byte Order Conversion -- Kyle Kloepper

By Blog Staff | Mar 19, 2013 12:08 PM | Tags: None

A new WG21 paper is available. A copy is linked below, and the paper will also appear in the next normal WG21 mailing. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N3620

Date: 2013-03-18

Network Byte Order Conversion

by Kyle Kloepper

Excerpt:

This proposal adds support to C++ for converting between host and network byte order.

New paper: N3619, A Proposal to Add Swappability Traits to the Standard Library -- Andrew Morrow

By Blog Staff | Mar 19, 2013 12:07 PM | Tags: None

A new WG21 paper is available. A copy is linked below, and the paper will also appear in the next normal WG21 mailing. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N3619

Date: 2013-03-15

A Proposal to Add Swappability Traits to the Standard Library

by Andrew Morrow

Excerpt:

This proposal proposes the addition of two new type property predicates to the C++ standard library: std::is_swappable<T, U = T> and std::is_nothrow_swappable<T, U = T>. 

 

New paper: N3618, What Can Signal Handlers Do? (CWG 1441) -- Hans-J. Boehm

By Blog Staff | Mar 19, 2013 12:04 PM | Tags: None

A new WG21 paper is available. A copy is linked below, and the paper will also appear in the next normal WG21 mailing. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N3618

Date: 2013-03-17

What Can Signal Handlers Do? (CWG 1441)

by Hans-J. Boehm

Excerpt:

CWG Issue 1441 points out that in the process of relaxing the restrictions on asynchronous signal handlers to allow use of atomics, we inadvertently made it impossible to use even local variables of non-volatile, non-atomic type. As a result of an initial discussion within CWG, Jens Maurer generated a proposed resolution, which addresses that specific issue.

Later discussion in SG1, both in Portland and during the February 2013 SG1 teleconference, raised a number of additional issues. Both Jens' solution and all prior versions of the standard still give undefined behavior to code involving signal handlers which we believe should clearly be legal. For example, a signal handler should be allowed to access "read-only" data that has not been modified since the signal handler was installed. Our goal is to correct such oversights, and allow some realistic signal handlers to be portable, while preserving a significant amount of implementation freedom with respect to what is allowable in a signal handler. In particular, we do not want to reinvent Posix' notion of async-signal-safe functions here.

...

We give several proposed changes and summarize the reasoning behind the change as well as some of the past discussion: ...