I am trying to investigate the issue with float I/O test that Vicente reported. But I am stuck.
Preliminary: I have not used clang before and I'm a beginner with building boost.
I started my Ubuntu x86_64 machine and checked out the trunk. I can successfully build trunk with b2 and GCC 4.5. I can also successfully run the multiprecision tests with GCC 4.5.
But even though clang 2.9 gets invoked, it can't find all of the C++ standard library. It seems to default to using the LINUX default includes and tries to use GCC's library headers.
I believe clang does use GCC's std lib headers on Linux - it always has for me - but like you I know almost nothing about Clang. This may be the problem actually - on the Mac, I believe Clang uses the libc++ as the standard lib, but that's only supported on the Mac :-( John.