N4595: WG21 2016-06-10 Telecon Minutes -- Jonathan Wakely

By Blog Staff | Jun 15, 2016 07:26 PM | Tags: None

A new WG21 paper is available. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N4595

Date: 2016-06-15

WG21 2016-06-10 Telecon Minutes

by Jonathan Wakely

2016-06 Pre-Oulu mailing available

By Blog Staff | Jun 3, 2016 09:26 AM | Tags: None

The 2016-06 mailing of new standards papers is now available.

NOTE: A number of these papers have already been publicized on this blog. This is the complete list including ones not previously publicized.

Jacksonville C++ Core Language Meeting Report--Jason Merrill

By Adrien Hamelin | May 19, 2016 01:30 PM | Tags: experimental

Here are the latest news about the future of C++:

Jacksonville C++ Core Language Meeting Report

by Jason Merrill

From the article:

There were three of us from Red Hat at the C++ meeting in Jacksonville, FL back in February, and it seems I never posted my trip report. So here it is now.

This was a fairly eventful meeting, as we’re rapidly approaching C++17 and so the big question on everyone’s minds was “What’s going to make it in?” In the end, many things did, but not Concepts, which some had been hoping for as a headline item.

We started and finished the week looking at the list of Technical Specifications that we were considering incorporating into C++17...

N4591: WG21 telecon meeting: Pre-Oulu -- Herb Sutter

By Blog Staff | May 19, 2016 10:48 AM | Tags: None

A new WG21 paper is available. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N4591

Date: 2016-05-19

WG21 telecon meeting: Pre-Oulu

by Herb Sutter

The status of reflection in C++ -- Axel Naumann

By Axel | Apr 19, 2016 03:08 PM | Tags: None

Axel Naumann writes about the state of the reflection in C++ in his recent article.

The status of reflection of C++

by Axel Naumann

From the article:

When the C++ committee met in Jacksonville two months ago, something big happened: the reflection study group, SG7, decided what the basic “language" of reflected C++ should look like. What does that mean? Why do you care? Let me, the co-author of the only “blessed proposal", explain...

C++ in Competitive Programming: warmup--Marco Arena

By Marco Arena | Apr 15, 2016 04:26 AM | Tags: basics

In this new post on Competitive Programming I introduce std::vector and std::accumulate:

C++ in Competitive Programming: warmup

by Marco Arena

From the article:

You are given an array of integers of size N. Can you find the sum of the elements in the array? ...

N4590: PL22.16/WG21 draft agenda: 20-25 Jun 2016, Oulu, FI -- Clark Nelson

By Blog Staff | Apr 12, 2016 01:11 PM | Tags: None

A new WG21 paper is available. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N4590

Date: 2016-04-07

PL22.16/WG21 draft agenda: 20-25 Jun 2016, Oulu, FI

by Clark Nelson

Excerpt:

Meeting objectives The primary goals of this meeting will be:

• Approve a CD for C++17
• Advance Library Fundamentals v2 toward TS
• Advance Networking toward PDTS
• Advance Parallelism v2 toward PDTS
• Advance Ranges toward PDTS

2016-03 Post-Jacksonville mailing available

By Blog Staff | Apr 2, 2016 03:23 PM | Tags: None

The 2016-03 mailing of new standards papers is now available.

NOTE: A number of these papers have already been publicized on this blog. This is the complete list including ones not previously publicized.

PO4116r0: Completing support for emotive programming in C++ -- Pablo Halpern

By Blog Staff | Apr 1, 2016 02:00 AM | Tags: None

A new WG21 paper is available. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: PO4116r0

Date: 2016-04-01

Completing support for emotive programming in C++

by Pablo Halpern

Excerpt:

There can be no doubt that C++ is an unusually expressive language. A significant part of that expressiveness comes from the ability to use emoticons, not just in comments and string literals, but in the code itself. For example the following (do-nothing) program compiles, links, and runs in all versions of C++: ...

P3141: std::terminates()

By Blog Staff | Apr 1, 2016 01:00 AM | Tags: None

A new WG21 paper is available.

Document number: P3141

Date: 2016-04-01

std::terminates()

by Hal T. Ng, Professor, C.S., LLVM.edu

Excerpt:

In 2014, the C++ committee tackled the problem of C++98's subtly hard-to-use std::uncaught_exception(), which was intended to return whether there were unhandled exceptions but did not work as intended in all destructor cases. The committee successfully addressed the problem by providing the improved std::uncaught_exceptions() (note plural "s"), which returns the number of unhandled exceptions in the current thread, and this function can now be used to reliably implement scope_guard and similar patterns in portable code.

Continuing in the same vein, this paper proposes to address C++98's related and sometimes-problematic std::terminate(). As its name suggests, the function causes abrupt program halts, which can cause data corruption if operations in flight are not completed gracefully. The set_terminate_handler() facility only partly addresses this problem by allowing a last-ditch handler to be invoked after unstoppable termination has already begun.

Along the same lines as conditional noexcept (noexcept(cond)), we propose a way for a sensitive operation, or a whole program, to determine in advance whether termination is possible. A program can test this by calling:

namespace std {
    bool terminates();
}

which returns true if and only if the program can subsequently terminate.

Because this function cannot fail to determine a valid result, it should be noexcept. Further, anticipating its usefulness in constant expressions and following LWG’s guidance for using constexpr wherever possible throughout the standard library, we propose in full:

namespace std {
    constexpr bool terminates() noexcept;
} 

Implementation notes: This function is so simple to specify that we foresee no implementation difficulty in any of the major C++ compilers.

Note that this is not the same as the halting problem, which would be to return true if and only if the program will halt, and which is known to take several hours to compute for programs longer than a few tens of millions of lines. Rather, this function is carefully constructed to return true if and only if the program could terminate, which is fundamentally different and well understood problem.

Acknowledgments: This paper expands on the core idea that was first proposed in committee hallway discussion by P.J. Plauger.