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CWG2999 Trivial unions changing existing behavior #2418

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cplusplus/draft
#8888
Closed
CWG2999 Trivial unions changing existing behavior#2418
cplusplus/draft
#8888
Labels
C++26Targeted at C++26CWGCorenb-commentThis paper is referenced in a NB comment
Milestone
2026-telecon

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@jensmaurer
jensmaurer
opened on Sep 11, 2025

The changes applied by P3074R7 for C++26 alter existing well-defined behavior for template arguments.

It is unclear whether such changes were design-intended.

See CWG2999 for details.

See also P3726R0 (Adjustments to Union Lifetime Rules) #2356.

Activity

  1. jensmaurer
    added this to the 2025-telecon milestone on Sep 11, 2025
  2. jensmaurer
    added
    EWGEvolution
    C++26Targeted at C++26
    on Sep 11, 2025

  3. jensmaurer commented on Nov 6, 2025

    @jensmaurer
    jensmaurer
    on Nov 6, 2025
    MemberAuthor

    EWG in Kona:

    See P3726 R0 Adjustments to Union Lifetime Rules #2356
    and the decisions documented in cplusplus/nbballot#664

  4. jensmaurer
    added
    CWGCore
    and removed
    EWGEvolution
    on Nov 6, 2025
  5. github-project-automation
    moved this to Ready for review in CWGon Nov 6, 2025
  6. github-project-automation
    added this to CWGon Nov 6, 2025
  7. jensmaurer
    modified the milestones: 2025-telecon, 2026-telecon on Jan 5, 2026
  8. jensmaurer
    added
    nb-commentThis paper is referenced in a NB comment
    on Mar 23, 2026
  9. tkoeppe
    closed this as completedin draft#8888on Apr 12, 2026
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