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From: Paul Van Delst <Paul.vanDelst@noaa.gov>
Newsgroups: comp.lang.ada,comp.lang.fortran
Subject: Re: Bounds Check Overhead
Date: Fri, 26 May 2006 15:23:22 -0400
Organization: CIMSS@NOAA/NCEP/EMC
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Xref: g2news2.google.com comp.lang.ada:4510 comp.lang.fortran:10309
Date: 2006-05-26T15:23:22-04:00
List-Id: <comp.lang.ada>

Richard Maine wrote:
> Nasser Abbasi <nma@12000.org> wrote:
> 
> 
>><about loop counters being changed.>
>>
>>I am not sure if there is supposed to compiler flag to enforce this or not,
> 
> 
> I said
> 
> 
>>Compilers are not required to enforce that rule,
> 
> 
> (In context, I meant Fortran compilers, as I do in all cases below.) In
> terms of the standard, that is basically all there is to say. As I tried
> to elaborate, almost all compilers do enforce simpe cases. I don't know
> of a compiler that doesn't. However, that has nothing to do with any
> requirement of the standard.
> 
> The standard has nothing at all to say about compiler switches in any
> context. That is not a concept defined by the standard.
> 
> 
>>so I did this very simple test,
> 
> 
> 
> No, this is not a simple test. This is one of the complicated cases. The
> code is short, but that doesn't necessarily mean simple to diagnose.

For the OP, here's both cases, and the simple one is caught:

PROGRAM testit
   IMPLICIT NONE
   INTEGER :: i
   DO i=1,10
     CALL foo(i)   ! The complicated case
     PRINT *,i
     i = i+2       ! The simple case
     PRINT *,i
   END DO
CONTAINS
   SUBROUTINE foo(i)
     INTEGER,INTENT(IN OUT) :: i
     i=i+1
   END SUBROUTINE foo
END PROGRAM testit

lnx:scratch : gfortran testit.f90
  In file testit.f90:7

     i = i+2
           1
  In file testit.f90:4

   DO i=1,10
           2
Error: Variable 'i' at (1) cannot be redefined inside loop beginning at (2)

(g95, lf95, and pgf95 give essentially the same error message.)


cheers,

paulv

-- 
Paul van Delst             Ride lots.
CIMSS @ NOAA/NCEP/EMC               Eddy Merckx
Ph: (301)763-8000 x7748
Fax:(301)763-8545