https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105284
Bug ID: 105284 Summary: missing syncstream and spanstream forward decl. in <iosfwd> Product: gcc Version: 12.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: cooky.ykooc922 at gmail dot com Target Milestone: --- according to https://wg21.link/iosfwd.syn's <iosfwd> sypnosis: The followings are declared (forward declaration only) which are added in C++20 and C++23: * class template std::basic_spanbuf * typedef std:spanbuf * typedef std::wspanbuf * class template std::basic_ispanstream * typedef std::ispanstream * typedef std::wispanstream * class template std::basic_ospanstream * typedef std::ospanstream * typedef std::wospanstream * class template std::basic_spanstream * typedef std::spanstream * typedef std::wspanstream * class template std::basic_syncbuf * typedef std::syncbuf * typedef std::wsyncbuf * class template std::basic_osyncstream * typedef std::osyncstream * typedef std::wosyncstream However, they are currently not added in the current header <iosfwd> of libstdc++