+On FreeBSD/x86 6.4, they represent the incorrect 53-bit precision assumptions
+in the compiler, not the real 64-bit precision at runtime.
+On Linux/PowerPC with GCC 4.4, on AIX 7.1 with GCC 4.2, and on IRIX 6.5,
+they don't reflect the ``double double'' representation of @code{long double}
+correctly.