2411. shared_ptr is only contextually convertible to bool

Section: 23.11.3 [util.smartptr.shared] Status: C++17 Submitter: Jonathan Wakely Opened: 2014-06-21 Last modified: 2017-07-30

Priority: 0

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Discussion:

N3920 made this edit, which is correct but unrelated to the support for arrays:

Change 20.7.2.2 [util.smartptr.shared] p2 as follows:

Specializations of shared_ptr shall be CopyConstructible, CopyAssignable, and LessThanComparable, allowing their use in standard containers. Specializations of shared_ptr shall be contextually convertible to bool, allowing their use in boolean expressions and declarations in conditions. […]

That change is actually fixing a defect in the current wording and should be applied directly to the working paper, not just to the Library Fundamentals TS. The declarations of the conversion operator in 23.11.3 [util.smartptr.shared] and 23.11.3.5 [util.smartptr.shared.obs] are explicit which contradicts the "convertible to bool" statement. The intention is definitely for shared_ptr to only be contextually convertible to bool.

[Urbana 2014-11-07: Move to Ready]

Proposed resolution:

This wording is relative to N3936.

  1. Change 23.11.3 [util.smartptr.shared] p2 as indicated:

    -2- Specializations of shared_ptr shall be CopyConstructible, CopyAssignable, and LessThanComparable, allowing their use in standard containers. Specializations of shared_ptr shall be contextually convertible to bool, allowing their use in boolean expressions and declarations in conditions. The template parameter T of shared_ptr may be an incomplete type.