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nonIEEEconform floats

Question asked by Fabian Kirsch on Nov 16, 2009
Latest reply on Nov 16, 2009 by CompilerGuru



working with CW 6.1 and a MC13213 i ran into problems with the floatingLib.

I constructed a snippet  that brings up the kind of problem. (even in the true-time-simulation)

I calculate x3 = (2.5e-11) - (1.7e-20)*(1.7e-20).

and would expect one of the following:

2.5e-11 (plus minus some rounding error), or NaN, or +Inf , or -Inf.

But I get: x3==-3.34...e+37


And this is not conform to IEEE 754 as far as i can see.


I already tried using a Service Request, but it got closed.

And i have no solution to the problem yet.


Q1: are you able to reproduce the behavior?

Q2: can you understand, why i expect a different result?

Q3: is this conform to IEEE in your opinion?

Q4: do you know a solution?

Aswers to any of these Questions is welcome.


many thanks



 int main(){
     volatile float x1;
     volatile float x2a;
     volatile float x2;
     volatile float x3;
     x1=2.5e-11; /** this is within normalized range **/
     x2a=1.7e-20; /** this is within normalized range **/
     x2 = x2a*x2a; /** this is within denormalized IEEE754
range **/
     x3=x1-x2;     /** this goes wrong i think **/

     while( x3<0 ); /** this halts, but should not **/

          for(;:smileywink:; /** this should halt but is never reached **/