Jay, I can reproduce with -O2 and -O3. See http://bb.pgr.jp/builders/cmake-llvm-x86_64-linux/builds/185 gcc version 4.4.4 20100726 (Red Hat 4.4.4-13) (GCC) The failures could be suppressed with -O2 -fno-strict-aliasing. I am dubious to type punning in ADT/Hashing.h. ...Takumi