[Bug fortran/57749] -ffpe-trap=zero or invalid produces SIGFPE on complex zero ** 1e0

["anlauf at gmx dot de" <gcc-bugzilla at gcc dot gnu dot org>]

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.