[Boost-bugs] [Boost C++ Libraries] #12235: boost/endian causes reads from unaligned address.

Subject: [Boost-bugs] [Boost C++ Libraries] #12235: boost/endian causes reads from unaligned address.
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2016-05-30 16:59:16

#12235: boost/endian causes reads from unaligned address.
-----------------------+------------------------------
 Reporter:  amotsok@…  |       Type:  Bugs
   Status:  new        |  Milestone:  To Be Determined
Component:  None       |    Version:  Boost 1.61.0
 Severity:  Problem    |   Keywords:
-----------------------+------------------------------
 Example:

 {{{
 #include <boost/endian/arithmetic.hpp>

 int main()
 {
   char __attribute__ ((aligned (4))) buf[20];

   boost::endian::native_int32_t * ptr = (boost::endian::native_int32_t
 *)&buf[1];

   return ptr->value();
 }

 }}}

 when stepping inside ''boost::endian::native_int32_t::value()'' I see the
 code which is doing actual work:
 {{{
   return *reinterpret_cast<T const *>(bytes);
 }}}

 where ''bytes'' is argument which corresponds to class member of
 ''endian_buffer'' which declared as:

 {{{
   char m_value[n_bits/8];
 }}}

 In this particular example ''m_value'' gets address ''buf + 1'' and it is
 not dividable by four:
 {{{
   (int)ptr->m_value & 3 == 1
 }}}

 Not all platforms support reading from unaligned address. This behavior is
 dangerous and possibly can cause crashes on those platforms.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/12235>
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