boost/endian causes reads from unaligned address.

[amotsok@…]

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.

[Beman Dawes]

The code you are complaining about is inside this:

# if defined(x86_64)

defined(_M_X64)

defined(i386)

defined(_M_IX86)

On x86 (which is little endian), unaligned loads are permitted

so is only reached on machines which permit unaligned loads.

--Beman