The <syncstream> header is only supported for the cxx11 ABI. The
declarations of basic_syncbuf, basic_osyncstream, syncbuf and
osyncstream were already correctly guarded by a check for
_GLIBCXX_USE_CXX11_ABI, but the wsyncbuf and wosyncstream declarations
were not.
libstdc++-v3/ChangeLog:
* testsuite/27_io/headers/iosfwd/synopsis.cc: Make wsyncbuf and
wosyncstream depend on _GLIBCXX_USE_CXX11_ABI.
(cherry picked from commit f9f05e483984bf89fec7778aaa55ece8ba2a86bb)
Jonathan Wakely
d2c737c40c