On Thu, 11 Jan 2018, 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.
As per previous IRC discussion, changing the lexing to support this pp-token can break valid code in previous standards, e.g. code concatenating <=> and >, then stringizing the result (the C++ proposal for adding this feature also notes some obscure cases where the character sequence <=> can actually occur as tokens, not just pp-tokens - "X<&Y::operator<=>" and "x+&operator<=>y" - so of course patches adding this feature should add testcases using such cases with older -std= options). Changes to cpp_avoid_paste (so that preprocessed output does not put a pp-token starting with > immediately after <=) do not need to be conditional on the standard version, however. -- Joseph S. Myers jos...@codesourcery.com
