Error using null_buffers in async_send_to in Windows

[nythil@…]

While exploring the boost.asio library I came across a bug caused by a typo in one of the header files. When async_send_to is invoked on an UDP socket with null_buffers, the following sequence of calls takes place:

1. basic_datagram_socket->async_send_to(const ConstBufferSequence& buffers, const endpoint_type& destination, WriteHandler handler)
2. datagram_socket_service->async_send_to(implementation_type& impl, const ConstBufferSequence& buffers, const endpoint_type& destination, socket_base::message_flags flags, WriteHandler handler)
3. win_iocp_socket_service->async_send_to(implementation_type& impl, const ConstBufferSequence& buffers, const endpoint_type& destination, socket_base::message_flags flags, Handler handler)

The problem is, the 3rd function is the generic version of async_send_to() which expects a valid buffer. Passing null_buffers causes an error.

There is also a specialization of async_send_to() for the null_buffers case. Unfortunately, it's never called, because in the declaration some arguments are out of place. The declaration is: async_send_to(implementation_type& impl, const null_buffers&, socket_base::message_flags, const endpoint_type&, Handler handler). Compared to the generic version, the flags and destination arguments are swapped. After correcting the order of these two arguments, async_send_to() works as expected.

[anonymous]

Thanks for the report. I see that the problem also applies to non-windows platforms.

Note that async_send_to/null_buffers isn't especially useful anyway. You can just use async_send instead, as the destination is ignored in any case.

[chris_kohlhoff]

(In [62644]) Merge from trunk.

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r62497 | chris_kohlhoff | 2010-06-07 09:28:58 +1000 (Mon, 07 Jun 2010) | 2 lines

Fix handling of small but non-zero timeouts. Fixes #4205.

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r62499 | chris_kohlhoff | 2010-06-07 10:00:45 +1000 (Mon, 07 Jun 2010) | 2 lines

Reworked implementation MkII. Also fixes #4170.

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r62530 | chris_kohlhoff | 2010-06-08 09:24:28 +1000 (Tue, 08 Jun 2010) | 2 lines

Fixes for MSVC 7.1, Borland.

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r62531 | chris_kohlhoff | 2010-06-08 09:29:05 +1000 (Tue, 08 Jun 2010) | 2 lines

Some changes for Symbian support.

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r62549 | chris_kohlhoff | 2010-06-08 14:27:26 +1000 (Tue, 08 Jun 2010) | 2 lines

Fix typo in tutorial. Fixes #4252.

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r62556 | chris_kohlhoff | 2010-06-08 19:01:39 +1000 (Tue, 08 Jun 2010) | 2 lines

Ensure unsigned char is used with isdigit. Fixes #4201.

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r62558 | chris_kohlhoff | 2010-06-08 21:01:57 +1000 (Tue, 08 Jun 2010) | 2 lines

Fix handling of empty buffer sequences.

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