[Bug fortran/38188] New: Inconsistent function results depending on irrelevant write statement

[Andrew Thomas Pinski]

I don't think INF is the same as infinity. It is most like implict  
declared variable with an undefined value.

Sent from my iPhone

On Nov 19, 2008, at 10:52 PM, "dojo at masterleep dot com" <gcc-bugzilla@gcc.gnu.org 
 > wrote:

> I am getting unreliable results from a small function using the latest
> prepackaged Mac OS build (PPC) available from the wiki download  
> page.  The
> function behaves correctly if an otherwise irrelevant write  
> statement is added.
> When the statement is removed, the function returns gibberish.  This  
> is
> ancient code which worked on older versions of gfortran, so  
> hopefully I haven't
> overlooked an obvious problem...
>
> $ uname -a
> Darwin Numenor 9.5.0 Darwin Kernel Version 9.5.0: Wed Sep  3  
> 11:29:43 PDT 2008;
> root:xnu-1228.7.58~1/RELEASE_I386 i386
>
> $ gfortran --version
> GNU Fortran (GCC) 4.4.0 20080823 (experimental) [trunk revision  
> 139508]
>
> $ cat xx.f
>        program xx
>        real xa(102)
>        do 10 i=1,100
> 10      xa(i)=float(i)
>        call scale (xa,23.,100,1)
>        write (*,*) xa(101), xa(102)
>        end
>
>
>        subroutine scale(arr,axlen,npts,kcycle)
>        real :: arr(*),axlen,minval,maxval,val
>        integer :: npts,kcycle
>        minval = +INF
>        maxval = -INF
>        do i=0,npts-1
>                val=arr(1+kcycle*i)
>                minval=amin1(val,minval)
>                maxval=amax1(val,maxval)
>        end do
>        arr(npts*kcycle+1)=minval
>        arr(npts*kcycle+kcycle+1)=(maxval-minval)/axlen
> c       If the following line is uncommented, the function will work
> c       write (*,*) 3
>        end subroutine scale
>
>
> # Correct function result (write statement is left in)
> $ gfortran -o xx xx.f
> $ xx
>           3
>   0.0000000       4.3478260
>
> # Incorrect function result (write statement is commented out)
> $ gfortran -o xx xx.f
> $ xx
> -2.13906214E+09  1.86005408E+08
>
>
> -- 
>           Summary: Inconsistent function results depending on  
> irrelevant
>                    write statement
>           Product: gcc
>           Version: unknown
>            Status: UNCONFIRMED
>          Severity: major
>          Priority: P3
>         Component: fortran
>        AssignedTo: unassigned at gcc dot gnu dot org
>        ReportedBy: dojo at masterleep dot com
>
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38188
>