Constexpr Library Additions: future

ISO/IEC JTC1 SC22 WG21 N3230 = 10-0220 - 2010-11-24

Benjamin Kosnik, bkoz@redhat.com

Jonathan Wakely, jwakely.gcc@gmail.com

Addresses: LWG 2013

Introduction

This paper details use of the ISO C++0x constexpr feature, as initially introduced in “Generalized Constant Expressions — Revision 5” (N2235) and incorporating all other subsequent changes as per ISO C++ draft N3126. Several CWG issues also influence the language with respect to constexpr: see issues 1099, 1125, 1194, 1195, 1197, 1198, 1199 and c++-std-core postings number 17890 and 17912. Additional implementation experience has motivated the following changes and additions to the library specification.

Proposed Changes

Add the following:

        - Mark default constructors of future constexpr.

        - Mark default constructors of shared_future constexpr.

Proposed wording

a) Modify 30.6.6  as follows:

constexpr future();

b) Modify 30.6.7  as follows:

constexpr shared_future();