id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
8295	`libs/asio/test/buffer.cpp` might fail because of an undefined behavior	Ai Azuma <ai.azuma@…>	chris_kohlhoff	"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.
"	Bugs	closed	To Be Determined	asio	Boost 1.53.0	Problem	fixed