https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70117
--- Comment #7 from Ulrich Weigand <uweigand at gcc dot gnu.org> --- Ah, OK. I did't realize this value didn't fit into a 106-bit mantissa. I agree that it probably doesn't make sense to change the internal representation to allow larger mantissas. First of all, there's nothing really special about 107 bits; there can be IBM long double values that would require a much larger mantissa in the internal representation, since we can have many implicit zero bits. But more problematical, if we change the internal representation to a mantissa larger than 106 bits, there will be values in that internal format that cannot be represented directly in the target IBM long double format. In any case, I certainly agree that the is* routines for IBM long double should simply operate on the high double of the pair. I still think that it would be better for gnulib to use the same LDBL_MAX as GCC, which means gnulib should probably be changed to use the 106-bit value.
