http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51779
--- Comment #8 from Tim Williams <zippy at anl dot gov> 2012-01-07 20:24:20 UTC --- (In reply to comment #7) > FYI, the miscompilation of MPFR 3.1.0's tis support by clang is resolved in > Xcode 4.2.1. > This was radar://10291355, "Xcode 4.2 miscompiles tls support in MPFR 3.1.0". Thanks, Jack. I should've been more specific: I am using Xcode 4.2.1. I'll try recompiling mpfr, and maybe try configuring mpfr with --disable-thread-safe as Dominique suggested.