id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
13584	"boost beast flat buffer move ctor, move assign and swap all ""cancel"" a prepare()"	paul.d.rose@…	chris_kohlhoff	"The boost beast flat_buffer ""cancels"" any outstanding prepare() when being moved from or swapped.

This seems like a very sane thing to do.

However, boost::asio::async_read_until depends on calling prepare() on it's DynamicBuffer and then calling the corresponding commit() on a moved-to version.

Flat buffer will (correctly) silently commit the minimum of the requested size and the size from the previous prepare().   When used with async_read_until, the commit is always zero, since the prepare was ""cancelled"" by the move.

The flat_buffer code always sets last_ to out_ during a move or swap, which is what achieves what I am calling the ""cancel"" of the prepare().

I tested setting last_ to other.last_ in the move ctor, move assignment, and swap, and verified that asio::async_read_until now works with beast::flat_buffer
  
On this report I set component=asio, because I couldn't find beast on the drop box.

I'm working with 1.67 and g++ 7.30 on ubuntu 18.04

"	Bugs	new	To Be Determined	asio	Boost 1.67.0	Problem		beast