September 2013 : Standard C++

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September 2013

New paper: N3717, SG5: Transactional Memory (TM) Meeting Minutes 2013/06/24-2013/08/26 -- M. Wong

By Blog Staff | Sep 9, 2013 08:35 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: N3717

Date: 2013-08-30

SG5: Transactional Memory (TM) Meeting Minutes 2013/06/24-2013/08/26

by Michael Wong

Excerpt:

Minutes for 2013/06/24 SG5 Conference Call

Minutes for 2013/07/08 SG5 Conference Call

Minutes for 2013/07/22 SG5 Conference Call

Minutes for 2013/08/05 SG5 Conference Call

Minutes for 2013/08/19 SG5 Conference Call

Minutes for 2013/08/26 SG5 Conference Call

New papers: N3713-15, Core Issues Lists -- William M. Miller

By Blog Staff | Sep 9, 2013 08:31 AM | Tags: None

Document number: N3713, N3714, N2715

Date: 2013-09-03

C++ Standard Core Language Active Issues, Revision 85

C++ Standard Core Language Defect Reports and Accepted Issues, Revision 85

C++ Standard Core Language Closed Issues, Revision 85

by William M. Miller

Excerpt:

The purpose of these documents is to record the disposition of issues that have come before the Core Language Working Group of the ANSI (INCITS PL22.16) and ISO (WG21) C++ Standard Committee.

New paper: N3712, Policy-Based Design for Safe Destruction in Concurrent Containers -- Arch Robison

By Blog Staff | Sep 9, 2013 08:27 AM | Tags: None

Document number: N3712

Date: 2013-08-30

Policy-Based Design for Safe Destruction in Concurrent Containers

by Arch Robison

Excerpt:

Writing containers that support concurrent access/modication by multiple threads incurs a special problem: when is it safe to delete an object? The problem is surprisingly tricky when lock-free operations are involved. Numerous general means have been proposed, ...

This paper sketches a way of abstracting these means so that concurrent container implementations could be parameterized over these means, thus allowing users to select the means best for their context. ...

This paper presents a sketch, not a complete proposal. It is intended to elicit discussion from experts as to whether the abstraction is viable. As such, this paper presents a fairly minimal interface that omits knobs for weak memory consistency and and extensive overloading of operators, so that experts can focus on a core question: Is the abstraction sufficient to support various means for deferred object deletion?

New paper: N3706, C++ Distributed Counters -- Lawrence Crowl

By Blog Staff | Sep 9, 2013 08:24 AM | Tags: None

Document number: N3706

Date: 2013-09-01

C++ Distributed Counters

by Lawrence Crowl

Excerpt:

We propose a set of coordinated counter types that collectively provide for distributed counting. The essential component of the design is a trade-off between the cost of incrementing the counter, the cost of loading (reading) the counter value, and the "lag" between an increment and its appearance in a "read" value. That is, the read of a counter value may not reflect the most recent increments. However, no count will be lost.

These counters are parameterized by the base integer type that maintains the count. Avoid situations that overflow the integer, as that may have undefined behavior. This constraint implies that counters must be sized to their use. (For dynamic mitigation, see the exchange operation below.)

LLVM Toolchain on Windows -- Chandler Carruth

By Eric Niebler | Sep 6, 2013 09:27 AM | Tags: None

Have you been waiting to use clang until it works on Windows? Your wait is over. The inimitable Chandler Carruth from Google announced an honest-to-god Windows installer for the LLVM toolchain that integrates into Visual Studio, and links with the native C++ runtime.

A Path Forward for an LLVM Toolchain on Windows

by Chandler Carruth

[...] we’ve been driving many of the efforts around compatibility with Visual Studio and native Windows C++ code in Clang and LLD (the LLVM linker). Today, as announced at my GoingNative 2013 talk, we are able to build a trivial C++ application that in turn links against native C++ libraries and uses them in real, interesting ways. This is a huge milestone for the project, and something we’re really excited to be talking more about.

Planetary: First Smithsonian curation of code created using C++ and Cinder-- S Chan & A Cope

By matt | Sep 5, 2013 12:23 PM | Tags: graphics creative coding cinder

The first piece of code acquired by the Smithsonian's Cooper-Hewitt National Design Museum -- "Planetary", written in C++.

Planetary: collecting and preserving code as a living object

Posted by Sebastian Chan & Aaron Cope on Monday August 26, 2013

From the article:

Cooper-Hewitt has just acquired its first piece of code. Although the collection has objects that are the end result of algorithmic processes, notably Patrick Jouin's 3D printed chair, Solid C2, this is the first time that code, itself, has been collected.

Almost all contemporary design practice involves digital processes -- from the ubiquitous Adobe design software to CAD packages used by product designers and architects, to the simple day-to-day office management and accounting software -- it would be difficult to find a designer who lives entirely 'off the grid.’ Despite this, design museums have been slow to start to add software to their permanent collections.

Some of this reticence to collect digital objects stems from deep uncertainties as to how to preserve and present such objects to future visitors and future scholars. But for Cooper-Hewitt these uncertainties have been a strong driver to experiment.

So, here we have Planetary.

Planetary is an iPad application written in C++ using the Cinder framework. Planetary offers an alternative music player application for the iPad that visualizes your music collection as a series of celestial bodies. Songs are moons, albums are planets, artists are suns—and the orbits of each are determined by the length of albums and tracks. Their brightness represents their frequency of playback.

Tales of C++ - Episode Six: Boollocks--K-ballo

By matt | Sep 3, 2013 10:12 AM | Tags: intermediate bool

Tales of C++, Episode 6:

Boollocks

by K-Ballo

From the article:

In the beginning there was no bool. And C++ said "let there be bool", and there was bool...

The Boolean data type is an integral type with only two values: true and false, intended to represent the truth values of logic and Boolean algebra. With only two values, what can possibly go wrong?

New paper: N3763, Traversable Arguments for Container Constructors and ..., Wording Rev 4 -- Yasskin

By Blog Staff | Sep 3, 2013 09:57 AM | Tags: None

Document number: N3763

Date: 2013-09-01

Traversable arguments for container constructors and methods, wording revision 4

by Jeffrey Yasskin

Excerpt:

The STL brought the notion of a range to C++, expressed as a pair of iterators. C++11 added the range-based for loop, which iterates over a single object for which begin(x) and end(x) return that pair of iterators. The Boost.Range library extends this to a full library of algorithms based on ranges as single objects. We don't yet know the full design of the library we want to standardize, but a simple step we already know is needed is to allow the output of that library to be passed to existing functions in the standard library that already take an iterator-pair range.

New paper: N3762, string_view: a non-owning reference to a string, revision 5 -- Jeffrey Yasskin

By Blog Staff | Sep 3, 2013 09:50 AM | Tags: None

Document number: N3762

Date: 2013-09-01

string_view: a non-owning reference to a string, revision 5

by Jeffrey Yasskin

Excerpt:

References to strings are very common in C++ programs, but often the callee doesn't care about the exact type of the object that owns the data. ...

Google, LLVM, and Bloomberg have independently implemented a string-reference type to encapsulate this kind of argument. string_view is implicitly constructible from const char* and std::string. It provides the const member operations from std::string to ease conversion. This paper follows Chromium and Bloomberg in extending string_view to basic_string_view<charT>, and further extends it to include a traits parameter to match basic_string. We provide typedefs to parallel the 4 basic_string typedefs.

Both Google's and LLVM's string_view types (but not Bloomberg's) extend the interface from std::string to provide some helpful utility functions:

starts_with

ends_with

remove_prefix

remove_suffix

split

trim

consume_prefix

count

Versions of std::string operations that take string_view instead also give the standard a way to provide in-place operations on non-null-terminated byte/character sequences:

hash, as requested by c++std-lib-31935

In a future addition, numeric conversions

New paper: N3766, The identity Type Transformation -- Jeffrey Yasskin

By Blog Staff | Sep 3, 2013 08:57 AM | Tags: None

Document number: N3766

Date: 2013-09-03

The identity type transformation

by Jeffrey Yasskin

Excerpt:

The need for the identity type transformation and backward-compatibility with the SGI library are still around, so this paper proposes two (mutually exclusive) options for nearly achieving both.