[Boost-users] [asio] strange behaviour on android

Subject: [Boost-users] [asio] strange behaviour on android
From: Igor R (boost.lists_at_[hidden])
Date: 2010-11-23 13:52:51

Hello,

Recently I ported my application to Android, and after some testing I
encountered the following strange behavior.
Long story short: I send text to a peer and sometimes it gets "cut" in
the beginning. like this: aaa\r\nbbb\r\nccc\r\nddd\r\n becomes
\nccc\r\nddd\r\n
I checked with sniffer, and ensured that the problem is really in my
application.

To send the text I use the following simple approach:
* io_service::run is always invoked from one thread
* the data comes from another thread and gets posted to the io_service thread:
void connection::send(const std::string &str)
{
  io_.post(boost::bind(&connection::doSend, shared_from_this(), str));
}

* then it's streamed into asio::streambuf:
void connection::doSend(const std::string &str)
{
  std::ostream(&output_).write(str.c_str(), str.length());
}

* and finally async_write is invoked, IF it's not in progress:
  if (!activeWrite_)
  {
    activeWrite_ = true;
    async_write(m_output, boost::bind(&connection::sent,
shared_from_this(), asio::placeholders::error));
  }

(of course, in sent() handler async_write is re-activated, if needed).

I understand that I add data to the streambuf, while async_write is in
progress, but it's done in the same thread, and seems to be
legitimate.
The above approach works on Windows and on some other platforms, it
was stress-tested, and never showed any problem. OTOH, on Android the
above issue happens very frequently (~20% of events).
The only difference here is that I compiled my project with
BOOST_ASIO_DISABLE_FENCED_BLOCK, because otherwise the linker
complains it doesn't see definitions of some gcc synchronization
intrinsics.
Is it possible that this's the problem? As far as I see, fenced_block
is used when a completion handler is called, so I can't see how it can
be connected to my problem...
Anyway, I'd appreciate any idea.

Thanks.