https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105284
--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-12 branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:3e6067bdcab5f677526d80325b9b8dc03f49024d commit r12-8364-g3e6067bdcab5f677526d80325b9b8dc03f49024d Author: Jonathan Wakely <jwak...@redhat.com> Date: Tue May 10 13:03:14 2022 +0100 libstdc++: Add <syncstream> declarations to <iosfwd> [PR105284] libstdc++-v3/ChangeLog: PR libstdc++/105284 * include/std/iosfwd: Add declarations for <synstream> class templates and typedefs. * include/std/syncstream (basic_syncbuf, basic_osyncstream): Remove default template arguments. * testsuite/27_io/headers/iosfwd/synopsis.cc: New test. * testsuite/27_io/headers/iosfwd/types.cc: New test. (cherry picked from commit 1807e07825a86916bbfddca470708c5a8f613612)