[Bug libfortran/48615] Invalid UP/DOWN rounding with E and ES descriptors

[thenlich at users dot sourceforge.net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48615

--- Comment #1 from Thomas Henlich <thenlich at users dot sourceforge.net> 2011-04-23 07:49:33 UTC ---
I think I found the problematic code in write_float:

  if (f->format == FMT_F || f->format == FMT_EN || f->format == FMT_G 
      || ((f->format == FMT_D || f->format == FMT_E)
      && dtp->u.p.scale_factor != 0))
    {
      /* Always convert at full precision to avoid double rounding.  */
      ndigits = MIN_FIELD_WIDTH - 4 - edigits;
    }
  else
    {
      /* The number of digits is known, so let printf do the rounding.  */
      if (f->format == FMT_ES)
    ndigits = f->u.real.d + 1;
      else
    ndigits = f->u.real.d;
      if (ndigits > MIN_FIELD_WIDTH - 4 - edigits)
    ndigits = MIN_FIELD_WIDTH - 4 - edigits;
    }

"let printf do the rounding" means the result will always be rounded according
to the rounding rules of printf, which is for GLIBC: "If the value being
printed cannot be expressed accurately in the specified number of digits, the
value is rounded to the nearest number that fits."