[Bug ada/18099] New: Incorrect rounding from floating point to integer

[bosch at gcc dot gnu dot org]

Ada requires conversion of floating-point to integer to round, with halfway cases rounded away from 
zero. This is implemented by adding 0.5 to the floating-point value and then truncating, as in regular C 
float to int conversion. However, this gives wrong semantics for the predecessor of 0.5, and odd 
floating-point integers in the range 2.0**(mantissa - 1)+1.0 .. 2.0**(mantissa)-1.0 and the negative 
versions of these.

The reason is that adding 0.5 in the above cases, yields a value exactly between two 
representable floating-point numbers. So the predecessor of 0.5 is then rounded to one, and the 
floating-point integers mentioned before get rounded to the next higher integer.

I'll file a self-contained test case testing these cases.

-- 
           Summary: Incorrect rounding from floating point to integer
           Product: gcc
           Version: 3.4.3
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P2
         Component: ada
        AssignedTo: bosch at gcc dot gnu dot org
        ReportedBy: bosch at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18099