------- Comment #6 from sgk at troutmask dot apl dot washington dot edu 2007-02-17 21:51 ------- Subject: Re: ICE with kind=8 exponentiaton
On Sat, Feb 17, 2007 at 09:27:07PM -0000, tkoenig at gcc dot gnu dot org wrote: > > > After looking at this a little bit, I think we may want to > > change the error message to report the invalid integer exponent > > value and document that INT_MIN <= e <= INT_MAX. Why? Well, > > other than the special values of 1 and 0, the evaluation of > > x**e will exceed the range of x. > > I don't think this is the case: > > $ cat foo.f90 > program main > real(kind=8) :: a > integer(kind=8) :: n > n = 2_8**32 > a = 1_8 + epsilon(a) > print *,a**n > end program main > $ gfortran foo.f90 > $ ./a.out > 1.00000095367477 > > I do admit this is a corner case, though :-) > OK, for numbers outside the nominal range of x in (1_8 - 1.651e-7_8, 1_8 + 1.651e-7_8), then x**e and e = INT_MAX you have problems. There is also a range (-f,f) with f << 1 where e could exceed the range [INT_MIN, INT_MAX]. I'm too lazy to determin f. Feel free to create a gfc_extract_long_long and document that e is constrained to be within [LONG_LONG_MIN, LONG_LONG_MAX]. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30834
