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Section: 26.6.6.2 [range.istream.view] Status: WP Submitter: Casey Carter Opened: 2021-06-15 Last modified: 2021-10-14
Priority: Not Prioritized
View all issues with WP status.
Discussion:
P2325R3 removes the default member initializers for basic_istream_view's exposition-only stream_ and value_ members. Consequently, copying a basic_istream_view before the first call to begin may produce undefined behavior since doing so necessarily copies the uninitialized value_. We should restore value_'s default member initializer and remove this particular footgun.
[2021-06-23; Reflector poll]
Set status to Tentatively Ready after seven votes in favour during reflector poll.
[2021-10-14 Approved at October 2021 virtual plenary. Status changed: Voting → WP.]
Proposed resolution:
Wording relative to the post-202106 working draft (as near as possible). This PR is currently being implemented in MSVC.
Modify 26.6.6.2 [range.istream.view] as indicated:
namespace std::ranges {
[…]
template<movable Val, class CharT, class Traits>
requires default_initializable<Val> &&
stream-extractable<Val, CharT, Traits>
class basic_istream_view : public view_interface<basic_istream_view<Val, CharT, Traits>> {
[…]
Val value_ = Val(); // exposition only
};
}