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CWG2784 Unclear definition of member-designator for offsetof #1616
Description
- Is a qualified-id allowed to appear in a member-designator?
- Is a template-id allowed to appear in a member-designator?
- Is an offsetof expression required to be a constant expression (7.7 [expr.const])?
See CWG2784 for details.
This issue lands right on the boundary of core and library specification, so EWG is asked to weigh in first, possibly deciding to involve L(E)WG.
Activity
hubert-reinterpretcast commentedon Sep 6, 2023
In C, it seems everything that can be applied after the
.token to get at a subobject is allowed. The questions may therefore extend to chains of.s and[]s.For C++, a question is whether
.*s with sufficiently-constant pointers-to-member is a bridge too far.erichkeane commentedon Nov 7, 2023
EWG discussed CWG2784 during the Tuesday Morning session in Kona. The following poll was taken.
CWG2784 "Unclear definition of member-designator for offsetof" this is an issue, we would like to see a paper which thoroughly explores the design space from and C++.
Result: Consensus
hanickadot commentedon Jun 24, 2024
EWG St. Louis: Alisdair Meredith volunteered to write a paper to turn
offsetofto keyword