[Bug fortran/57628] spurious error: division by zero in if statement

[sgk at troutmask dot apl.washington.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57628

--- Comment #17 from Steve Kargl <sgk at troutmask dot apl.washington.edu> ---
On Mon, Jun 17, 2013 at 10:07:32PM +0000, furue at hawaii dot edu wrote:
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57628
> 
> --- Comment #16 from Ryo Furue <furue at hawaii dot edu> ---
> (In reply to Steve Kargl from comment #12)
> > On Sun, Jun 16, 2013 at 11:33:49PM +0000, furue at hawaii dot edu wrote:
> > > 
> > > Is this an inconsistency in the implementation of -no-range-check ?
> > 
> > No.
> 
> Then, what's the counterpart of -fno-range-check that takes care of such cases
> as sqrt?  To repeat the code:
> 
>   real, parameter:: a = -1.0
>   if (a > 0) write(*,*) sqrt(a)
> 
> With such a switch turned on, the compiler can replace sqrt(-1.0) with NaN and
> let the code pass.
> 

Why not replace it with 0 instead of NaN?  Afterall, the real part
of the imaginary number i (or j if you're an electrical engineer)
is 0?

  13.7.159 SQRT(X)

  Argument.  X shall be of type real or complex.  Unless X is complex,
  its value shall be greater than or equal to zero.

Those "shall be" phrases are fair strong statements.

Yeah, I get it.  You don't like the choice that gfortran
made 10+ years ago.