Re: [Boost-users] [asio] io_service::run() asserting: "vector iterator not dereferencable"

Subject: Re: [Boost-users] [asio] io_service::run() asserting: "vector iterator not dereferencable"
From: Robert Dailey (rcdailey_at_[hidden])
Date: 2009-08-26 15:48:27

I figured out what my problem was. This was a container going out of
scope and being destroyed. The iterators that still existed in ASIO
were pointing to an invalid container.

---------
Robert Dailey

On Wed, Aug 26, 2009 at 1:09 PM, Robert Dailey<rcdailey_at_[hidden]> wrote:
> Inside of win_iocp_handle_service.write_operation.do_completion_impl(),
> there is this block of code (Note I'm using Boost 1.40 Beta):
>
>
> #if defined(BOOST_ASIO_ENABLE_BUFFER_DEBUGGING)
>       // Check whether buffers are still valid.
>       typename ConstBufferSequence::const_iterator iter
>         = handler_op->buffers_.begin();
>       typename ConstBufferSequence::const_iterator end
>         = handler_op->buffers_.end();
>       while (iter != end)
>       {
>         boost::asio::const_buffer buffer(*iter);
>         boost::asio::buffer_cast<const char*>(buffer);
>         ++iter;
>       }
> #endif // defined(BOOST_ASIO_ENABLE_BUFFER_DEBUGGING)
>
>
> The call to buffers_.begin() is causing the assert. Looks like a
> container is getting invalidated/corrupted somehow. I have no idea why
> this is happening. I'm calling io_service::run() from its own worker
> thread in a continuous loop like so:
>
>
>   for(;;)
>   {
>     boost::this_thread::sleep( boost::posix_time::milliseconds( 20 ) );
>     m_service.run();
>   }
>
>
> The class that is wrapping the io_service and serial_port objects
> invokes a post at construction (from the main thread), to start off a
> transparent yet continuous chain of reads over the serial port:
>
> m_service.post( boost::bind( &SerialClient::DoRead, this ) );
>
> After that, externally I call a function that posts a write in a
> similar way. This write occurs after the above post for the read:
>
> m_service.post( boost::bind( &SerialClient::DoWrite, this, data ) );
>
> When I step through the sequence of events, I see the following happen:
>
> - io_service and serial_port are constructed and initialized
> - io_service thread is started (But run() has not been called yet)
> - The DoRead() is posted to the io_service
> - The DoWrite() is posted to the io_service
> - io_service.run() is called from the worker thread for the first time
> - DoRead() is called from io_service::run(), which in turn calls
> serial_port::async_read_some()
> - DoWrite() is called from io_service::run(), which in turn calls
> boost::asio::async_write() on the serial_port
> - ReadCompleted() is invoked as the callback from the previous
> serial_port::async_read_some() call. It does NOT call async_read_some
> again (for testing, I disabled the looped reading).
> - After ReadCompleted() scope exits, it throws the assert
>
> Not sure what I'm doing wrong. Keep in mind that this whole time the
> COM port is not connected to anything, but I'm not sure if this will
> have anything to do with it. I've attached the code just in case you
> don't mind looking over it.
>
> ---------
> Robert Dailey
>