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: N3745

Date: 2013-08-28

Feature-testing recommendations for C++

by Clark Nelson

Excerpt:

[1] The more time that passes without any sort of feature-testing recommendation, the more confusion will affect programmers and implementers interested in features of C++14, of the sort that has plagued C++11 for years. So whatever action should be taken in this arena should not be delayed any more than can be avoided.

[2] SG10 intends to produce its recommendations solely as a WG21 document, without any balloting at higher levels. This is partly to save time, but also to avoid making significant conformance changes. It is hoped that compiler and library implementers will follow these recommendations voluntarily, even without the threat of claims of non-conformance. To improve the chances of that happening, it is considered important to have a record of the endorsement of WG21 -- or at least of the C++ technical experts who attend WG21 meetings.

[3] So SG10 would like to bring this document forward for some sort of approval vote at the Chicago meeting. Formally speaking, no action by the committee is requested, so this vote should probably be just a straw poll.

[4] It should be understood that section 2, “Recommendations” (excluding the sub-sections that are currently stubs), is the section for which approval and stability really matter. Improving the examples, or explanations of rationale, is basically editorial, and improvements will hopfully continue to happen after the recommendations themselves have been approved.

[5] Note that this document recommends that the __has_include feature be provided in the C++14 time frame, even though it is not included in the CD for C++14. A conceivable alternative would be to add __has_include to C++14 before its final publication.

[6] This revision of this document contains STUBS for sections expected to be filled in later.