`libs/asio/test/buffer.cpp` might fail because of an undefined behavior

[Ai Azuma <ai.azuma@…>]

The invocation of buffer_copy at line 173 in libs/asio/test/buffer.cpp might cause an undefined behavior. Therefore, the test case might fail in any reason even if the invocation is enclosed by a try block.

More specifically, this test case fails when compiling on GCC 4.8.0 with AddressSanitizer (-fsanitize=address). The error report created by AddressSanitizer is as follows;

=================================================================
==28915== ERROR: AddressSanitizer: memcpy-param-overlap: memory ranges [0x7fff9eceff20,0x7fff9ecf02a0) and [0x7fff9ecefea0, 0x7fff9ecf0220) overlap
    #0 __interceptor_memcpy at /home/cryolite/work/intro/gcc-4.8-20130310/libsanitizer/asan/asan_interceptors.cc:285
    #1 boost::asio::buffer_copy(boost::asio::mutable_buffer const&, boost::asio::const_buffer const&) at /home/cryolite/local/boost/latest/libs/asio/test/../../../boost/asio/buffer.hpp:1291
    #2 boost::asio::buffer_copy(boost::asio::mutable_buffers_1 const&, boost::asio::mutable_buffer const&) at /home/cryolite/local/boost/latest/libs/asio/test/../../../boost/asio/buffer.hpp:1466
    #3 buffer_compile::test() at /home/cryolite/local/boost/latest/libs/asio/test/buffer.cpp:173
    (The rest of the backtrace is omitted because they are essentially irrelevant.)

(The backtrace has been translated into corresponding source file lines.)

As the error report indicates, buffer_copy in line 173 comes down to memcpy between overlapped memory regions. This is ill-formed, and an undefined behavior might forbid the test case to continue.

In addition to this problem, the documentation for buffer_copy does not clearly mention whether the source and destination regions of buffer_copy can be overlapped or not. If it is not allowed as the implementation (the use of memcpy) indicates, it would be better to document it clearly.

[chris_kohlhoff]

Fixed on 'develop' in ​2114f2d17b535c53cf1f1ef086676335c87e388d and ​fd8471c5d69425f0fd47ab4bef604c197d30dabc.

Merged to 'master' in ​4e1e7d731fcc5c0104567856de476f7ce8806d72.