Section: 32.5.8 [atomics.types.generic] Status: Resolved Submitter: Anthony Williams Opened: 2008-09-26 Last modified: 2017-11-29
Priority: Not Prioritized
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Discussion:
Addresses US 90
The deleted copy-assignment operators for the atomic types are not marked as volatile in N2723, whereas the assignment operators from the associated non-atomic types are. e.g.
atomic_bool& operator=(atomic_bool const&) = delete; atomic_bool& operator=(bool) volatile;
This leads to ambiguity when assigning a non-atomic value to a non-volatile instance of an atomic type:
atomic_bool b; b=false;
Both assignment operators require a standard conversions: the
copy-assignment operator can use the implicit atomic_bool(bool)
conversion constructor to convert false to an instance of
atomic_bool, or b can undergo a qualification conversion in order to
use the assignment from a plain bool.
This is only a problem once issue 845 is applied.
[ Summit: ]
Move to open. Assign to Lawrence. Related to US 90 comment.
[ 2009-08-17 Handled by N2925. ]
[ 2009-10 Santa Cruz: ]
NAD EditorialResolved. Addressed by N2992.
Proposed resolution:
Add volatile qualification to the deleted copy-assignment operator of all the atomic types:
atomic_bool& operator=(atomic_bool const&) volatile = delete; atomic_itype& operator=(atomic_itype const&) volatile = delete;
etc.
This will mean that the deleted copy-assignment operator will require
two conversions in the above example, and thus be a worse match than
the assignment from plain bool.