Dear All, Can ARM support be added to detail/endian.hpp ? It's complicated by the fact that ARM systems may have either endianness. I believe that the symbols __ARMEL__ and __ARMEB__ are defined by gcc for the little- and big-endian cases respectively. However, it also seems that gcc defines __LITTLE_ENDIAN__; can we just test for that? There is possibly some confusion with __LITTLE_ENDIAN and __BIG_ENDIAN (no trailing __s) which I believe glibc defines both of as 4321 and 1234, but it should be OK to write: #elif defined(__LITTLE_ENDIAN__) && !defined(__BIG_ENDIAN__) ... I suspect someone has looked at this before. It can't do any harm to add all of the potential tests, can it? Thanks, Phil.