https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110311
--- Comment #16 from Jürgen Reuter <juergen.reuter at desy dot de> ---
It seems that it is this function where the NaNs appear:
function mult_mod (a, b, c, m) result (v)
real(default), intent(in) :: a
real(default), intent(in) :: b
real(default), intent(in) :: c
real(default), intent(in) :: m
real(default) :: v
integer :: a1
real(default) :: a2
v = a * b + c
if (v >= two53 .or. v <= -two53) then
a1 = int (a / two17)
a2 = a - a1 * two17
v = mod (a1 * b, m)
v = v * two17 + a2 * b + c
end if
v = mod (v, m)
if (v < 0.0_default) v = v + m
end function mult_mod
particularly mod (v, m) gets evaluated to NaN, even if a replace it with
v = mod (v0, m) to avoid potential aliasing problems. It appears only in a very
complex setup, not in a 100 line program.
