LWG 581 changed ostream::flush() to an unformatted output function for C++11, but it was never implemented in libstdc++. libstdc++-v3/ChangeLog: * doc/xml/manual/intro.xml: Document LWG 581 change. * doc/html/manual/bugs.html: Regenerate. * include/bits/basic_ios.tcc: Whitespace. * include/bits/ostream.tcc (basic_ostream::flush()): Construct sentry. * testsuite/27_io/basic_ostream/flush/char/2.cc: Check additional cases. * testsuite/27_io/basic_ostream/flush/char/exceptions_badbit_throw.cc: Likewise. * testsuite/27_io/basic_ostream/flush/wchar_t/2.cc: Likewise. * testsuite/27_io/basic_ostream/flush/wchar_t/exceptions_badbit_throw.cc: Likewise.