On 11 January 2018 at 10:13, Jonathan Wakely wrote: > t all cleaOn 11 January 2018 at 10:05, David Brown wrote: >> Maybe it is easier to say "gcc supports <=> in C++2a, and as an >> extension also supports it in C and C++ of any standard" ? I don't >> believe there is any way for it to conflict with existing valid code, so >> it would do no harm as a gcc extension like that - and C users can then >> use it too. > > It's not very useful in C because you need the comparison category > types, which are classes defined in <compare> (see > http://en.cppreference.com/w/cpp/header/compare) > > C doesn't have those types, and can't define anything close. > > And it's non-conforming to declare those types in pre-C++2a, because > the names could be used by user programs. > > Potentially the types could be defined with reserved names like > __strong_ordering, and then make std::strong_ordering a typedef for > that, but there are also changes to the language spec that go with the > new operator, and enabling those pre-C++2a could change the meaning of > valid code. > > So it's not ar it does no harm.
Sorry, Firefox keeps jumping the cursor around and garbled this text as I entered it. That should read: So it's not at all clear it does no harm.
