Document number: N3550

Date: 2013-03-12

Proposed C++14 Value Classification

by Walter Brown

Because the C++11 value classification scheme is widely distributed throughout the text of the standard, it seems unnecessarily difficult to assess the global impact of the direction suggested in the last paragraph of [CWG issue 1585]. We therefore propose a centralized specification of the scheme.

... Independent of the outcome of CWG 1585, we propose to centralize the specification of value classification, and correspondingly to excise the current widely distributed specifications.

Document number: N3549

Date: 2013-03-12

s/bound/extent/

by Walter Brown

The C++11 standard uses two distinct terms of art to denote an array’s number of elements. For the sake of consistency, as well as improved technical accuracy, this paper proposes to adopt a single term of art throughout the standard.

Document number: N3548

Date: 2013-03-12

Conditionally-supported Special Math Functions for C++14

by Walter Brown

This paper proposes to merge International Standard 29124:2010, “Extensions to the C++
Library to support mathematical special functions,” into C++14 as a conditionally-supported
standard library feature.

Document number: N3547

Date: 2013-03-12

Three <random>-related Proposals

by Walter Brown

This paper proposes (1) to add one function template to <algorithm>, (2) to add a few novice-friendly functions to <random>, and (3) to deprecate some related legacy interfaces. The unifying factor in this tripartite proposal is the entities’ respective connection with random numbers.

Document number: N3546

Date: 2013-03-12

TransformationTraits Redux

by Walter Brown

This paper proposes to augment C++11’s TransformationTraits with a number of template
aliases whose use dramatically simplifies the traits’ most common applications.

Document number: N3545

Date: 2013-03-12

An Incremental Improvement to integral_constant

by Walter Brown

This paper proposes to add a constexpr operator() to the synopsis of integral_constant
in order to allow the template to serve as a source of compile-time function objects.

Document number: N3537

Date: 2013-03-12

Clarifying Memory Allocation

by Lawrence Crowl and Chandler Carruth

The allocation and deallocation of memory has become a significant expense in modern systems. ...

An essential requirement on implementations is that they deliver usable memory, not that they have a particular sequence of calls. We propose to explicitly decouple the implementation calls from the abstract calls. ... Together these changes enable implementations to reduce the number of malloc calls by avoiding them or fusing them. However, it would only enable fusing mallocs together into larger mallocs provided it can prove that both mallocs have overlapping lifetimes (ended by corresponding calls to free) such that the peak allocated memory of the program remains unchanged.

Document number: N3533

Date: 2013-03-12

C++ Concurrent Queues

by Lawrence Crowl and Chris Mysen

This paper revises N3434 = 12-0043 - 2012-01-14 as follows.

• Add more exposition.

• Provide separate non-blocking operations.

• Add a section on the lock-free queues.

• Argue against push-back operations.

• Add a cautionary note on the usefulness of is_closed().

• Expand the cautionary note on the usefulness of is_empty(). Add is_full().

• Add a subsection on element type requirements.

• Add a subsection on exception handling.

• Clarify ordering constraints on the interface.

• Add a subsection on a lock-free concrete queue.

• Add a section on content iterators, distinct from the existing streaming iterators section.

• Swap front and back names, as requested.

• General expository cleanup.

• Add an 'Revision History' section.

Document number: N3532

Date: 2013-03-12

C++ Dynamic Arrays

by Lawrence Crowl and Matt Austern

Instead of adopting C variable-length arrays, we propose to define a new facility for arrays where the number of elements is bound at construction. We call these dynamic arrays, dynarray. In keeping with C++ practice, we wish to make dynarrays usable with more than just automatic variables. But to take advantage of the efficiency stack allocation, we wish to make dynarray optimizable when used as an automatic variable.

Document number: N3527

Date: 2013-03-10

A proposal to add a utility class to represent optional objects (Revision 3)

by Fernando Cacciola and Andrzej Krzemieński

Class template optional<T> proposed here is a type that may or may not store a value of type T in its storage space. Its interface allows to query if a value of type T is currently stored, and if so, to access it. The interface is based on Fernando Cacciola's Boost.Optional library, shipping since March, 2003, and widely used. It requires no changes to core language, and breaks no existing code.