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3127.basic_osyncstream::rdbuf needs a const_cast
Section: 31.11.3.1 [syncstream.osyncstream.overview] Status: C++20 Submitter: Tim Song Opened: 2018-06-29 Last modified: 2021-02-25
Priority: 0
View all other issues in [syncstream.osyncstream.overview].
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Discussion:
The current specification of basic_osyncstream::rdbuf() is
syncbuf_type* rdbuf() const noexcept { return &sb; }
This is ill-formed because the exposition-only member sb is const inside this const member function, but the return type is a pointer to non-const syncbuf_type. It needs to cast away the constness, consistent with the other streams with embedded stream buffers (such as string and file streams).
[2018-07-20 Status set to Tentatively Ready after five positive votes on the reflector.]
[2018-11, Adopted in San Diego]
Proposed resolution:
This wording is relative to N4750.
Change 31.11.3.1 [syncstream.osyncstream.overview], class template basic_osyncstream synopsis, as indicated:
namespace std {
template<class charT, class traits, class Allocator>
class basic_osyncstream : public basic_ostream<charT, traits> {
public:
[…]
// 31.11.3.3 [syncstream.osyncstream.members], member functions
void emit();
streambuf_type* get_wrapped() const noexcept;
syncbuf_type* rdbuf() const noexcept { return const_cast<syncbuf_type*>(&sb); }
[…]
};
}
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