Thanks for this bug report and patch! I believe this will affect the ABI, so I'm waiting for Warren's comments.

I think a better way to handle this would be to use the protected init() member. Regular streams like fstream and stringstream need to behave the same way as our Query, since they need to controll their own buf objects.

For example, they do (from g++ headers):

basic_ifstream() : __istream_type(NULL), _M_filebuf() { this->init(&_M_filebuf); }

This would prevent a change in the ABI.