http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57749
--- Comment #19 from Harald Anlauf <anlauf at gmx dot de> --- (In reply to Vittorio Zecca from comment #16) > You are being a little too hard on me, but so be it. > > I believe there is only one special case, base==0, > and that there are only two ifs to put in cpow to avoid the floating > exception > and give the expected result(I am simplifying here, also because I do > not use C): > > if(base==0) > { > if(exponent>0) return 0; else raise hell; > } > > The actual code where the original issue occurred had the exponentiation > in the deep of nested loops, it would have been rather time consuming > to test base==0 > at the Fortran level > > > And I still do not understand why if the exponent is integer no > exception is raised and > the expected result zero is delivered. > As in the following fragment (with option -ffpe-trap=zero,invalid): > complex x > x=cmplx(0e0,0e0) > i=2 > r=2e0 > print *,x**i ! no exception raised delivers zero > print *,x**r ! exception raised > end > The Intel ifort and NAG nagfor compilers raise no exceptions and > deliver the expected result. > With my best wishes of good work to everybody. You obviously haven't tried other compilers. With xlf, the result also depends on compiler flags: Either (0.,0.), (NaNQ,NaNQ), or Trace/BPT trap (core dumped) I think you should accept that your code invokes undefined behavior and needs fixing.