On 7/28/13 8:45 PM, "Larry Evans" <cppljevans@suddenlink.net<mailto:cppljevans@suddenlink.net>> wrote: I thought the filtering_stream would be derived from std::ostream, at least according to: Derived class of std::basic_istream, std::basic_ostream or std::basic_iostream, used to perform filtering. quoted from: http://www.boost.org/doc/libs/1_54_0/libs/iostreams/doc/classes/filtering_st... Did you not find this so, or do you needs require something more specific than std::ostream& to be passed to the other functions you mention? Larry -- Thanks! You would've thought that — and you know what? You would be CORRECT. I thought I had tested every possible case — but I think I did that BEFORE discovering my error with closing the file before destructing the filtering_streambuf/filtering_ostream. You (and everyone else) were ABSOLUTELY CORRECT. When I changed my code from a filtering_streambuf: ofstream myXMLFile (destPath, std::ios_base::out | std::ios_base::app | std::ios_base::binary); boost::iostreams::filtering_streambuf<boost::iostreams::output> filteringOStream; filteringOStream.push(boost::iostreams::zlib_compressor()); filteringOStream.push(myXMLFile); std::ostream myExportedXMLFilteringOStream(&filteringOStream); Foo(myExportedXMLFilteringOStream); TO A filtering_ostream: ofstream myXMLFile (destPath, std::ios_base::out | std::ios_base::app | std::ios_base::binary); boost::iostreams::filtering_ostream myExportedXMLFilteringOStream; myExportedXMLFilteringOStream.push(boost::iostreams::zlib_compressor()); myExportedXMLFilteringOStream.push(myXMLFile); Foo(myExportedXMLFilteringOStream); Thank you so much for tying up that loose end! I'm assuming the filtering_ostream is of course more efficient than the filtering_streambuf scenario? Best Regards, Stephen