Hi, The following causes an assertion failure (in iostreams::detail::optional::operator*()) when destroying the filtering_stream: #include <boost/iostreams/filtering_stream.hpp> #include <boost/iostreams/code_converter.hpp> #include <boost/iostreams/device/file_descriptor.hpp> #include <windows.h> namespace io = boost::iostreams; int main (void) { io::wfiltering_stream<io::output> out; HANDLE h = CreateFileW(L"test.txt", GENERIC_WRITE | GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_ALWAYS, 0, NULL ); out.push( io::code_converter<io::file_descriptor_sink>( io::file_descriptor_sink(h, true) ) ); out << L"Hello world!"; return 0; } If I add "out.pop()" before returning, there is no assertion. Looking deeper, it turns out that iostreams::chain's dtor calls close(); and reset();, and both end up calling close() on the code_converter. And code_converter is not "multi-closable". IOW, I get the same assertion failure with: HANDLE h = CreateFile(/*...*/); io::code_converter<io::file_descriptor_sink> cvt(io::file_descriptor_sink(h, true)); cvt.close(); cvt.close(); //<< Asserts here To fix this, I made it possible to call code_converter::close() multiple times by simply adding: if (!(this->is_open())){ return; } right at the beginning of code_converter::close(). Am I right in assuming that it should be possible to close() a Device or Filter multiple times ? Anyone has comments on this proposed fix? ----------------------------- Éric Quidquid latine dictum sit, altum viditur.