interesting segfault

I had a segmentation fault which is due to NaN. However, this was interesting because although the IF statement was always false, it gave me segfault because NaN would result if the IF statement was true.. 

        write(numout,*) 'hhpass: nancheck ',(1.-pfrld(ji,jj))/(1.-frld(ji,jj)+epsilon30)
        IF(frld(ji,jj)-pfrld(ji,jj) > 0.) THEN ! In case of accretion, newly formed ice will have a tracer concentration of an underlying seawater value.
          write(numout,*) 'hhpass: inside if statement'
          icechl(ji,jj) = icechl(ji,jj)/(trn(ji,jj,1,jpdch)+epsilon30)!((1.-pfrld(ji,jj))/(1.-frld(ji,jj)+epsilon30)*icechl(ji,jj) + ((1.-frld(ji,jj))-(1.-pfrld(ji,jj)))/(1.-frld(ji,jj)+epsilon30)*trn(ji,jj,1,jpdch)
        END IF


 Update: This seems to have to do with floating points.

Writing out the output for the variables in dinomenator and numerator show a particular floating point (i.e. 14):

 hhpass: pfrld    1.00000000000000
 hhpass: frld    1.00000000000000





In the example above, I tried avoid the division by zero by introducing epsilon number 30 (i.e. 1.e-30), but the division produced NaN:

hhpass: nancheck    NaN

After this, I instead introduced a epsilon number that is smaller than the floating point of the two variables (i.e. 4). Then the division produced zero:

 hhpass: nancheck   0.000000000000000E+000


Epsilon30 worked for biogeochemical tracers. But not for ice physical tracers (probably a specic floating point number is defined in LIM_SRC_2 for these tracers?)