Hi, I guess it is ok to ask about details even if the library isn't in review yet, right? I'm not an expert in architecture so I hope I'm not asking something obvious. My understanding is that for example if you're targetting classic PC hardware, you'll get BOOST_ARCHITECTURE_X86 for 32Bit OS BOOST_ARCHITECTURE_AMD64 for 64Bit OS (running on 64bit processor). That assume that the hardware have a "normal" Intel or AMD processor. Then if it doesn't, it can be other kind of architecture (ARM or other listed in the defines) Would it be possible to also provide macros that would tell what is the "bit size" (I don't know the correct word here) without the architecture name? Something like BOOST_ARCHITECTURE_BITS_32 BOOST_ARCHITECTURE_BITS_64 Again, maybe I'm being naive about this, but I'm thinking about code that should behave differently under those conditions and shouldn't have to check all the corresponding architecture macro to detect wether it's 32 or 64 bits. Anyway, it's a nice library that would allow me to not have to set some (certainly flawed) macro myself. Joël Lamotte