std::vector<int> v(1)Boost.Asio now takes advantage of this feature to add buffer debugging. Consider the following code:
std::vector<int>::iterator i = v.begin();
v.clear(); // invalidates iterators
*i = 0; // assertion!
void dont_do_this()When you call an asynchronous read or write you need to ensure that the buffers for the operation are valid until the completion handler is called. In the above example, the buffer is the
std::string msg = "Hello, world!";
asio::async_write(sock, asio::buffer(msg), my_handler);
msg. This variable is on the stack, and so it goes out of scope before the asynchronous operation completes. If you're lucky, your application will crash. Often you will get random failures.
With the new buffer debug checking, however, Boost.Asio stores an iterator into the string until the asynchronous operation completes, and then dereferences it to check its validity. In the above example you get an assertion failure just before Boost.Asio tries to call the completion handler.
This feature has only been tested with MSVC 8.0 so far, but it should work with any other implementation that supports iterator debugging. Obviously there's a performance cost to this checking, so it's only enabled in debug builds. You can also explicitly disable it by defining
ASIO_DISABLE_BUFFER_DEBUGGINGif you're using standalone asio).