[Bug fortran/33251] New: f77 reads one field into two variables in list directed i/o

[Bug fortran/33251] New: f77 reads one field into two variables in list directed i/o

[William dot Daffer at jpl dot nasa dot gov]

The problem is that the I/O system reads one (admittedly malformed)
field into two variables in list directed input.


Take this one line and put it in a file named 'the_test_file'

--------- cut --------- cut --------- cut --------- cut 
  13.5-1420.83   1    0.350E+00 -0.181E+19 
--------- cut --------- cut --------- cut --------- cut 


In the same directory, save the following code, compile and run...

--------- cut --------- cut --------- cut --------- cut 
      program showbug
      real*4 press,atemp,zalt,junk,therest
      integer readstat
      open (10, file='the_test_file',status='old')
      read(10,*,end=223,err=555,iostat=readstat) 
     &           zalt,atemp,junk,press, therest

 223  continue
 555  if (readstat.gt.0) then
        print *,'Error!'
        stop
      endif 

      print *,'No Error'
      print *,'zalt=',zalt,',atemp=',atemp,',junk=',junk
      print *,'press=',press,',therest=',therest
      end

--------- cut --------- cut --------- cut --------- cut 

I used g77 -o showbug showbug.f

When I ran this I got the following output.

--------- cut --------- cut --------- cut --------- cut 
% ./showbug
 No Error
 zalt=  0.,atemp=  0.829999983,junk=  1.
 press=  0.349999994,therest= -1.80999996E+18
--------- cut --------- cut --------- cut --------- cut 

The problem is that the I/O library reads that first string of
characters into *two* fields. Notice the value of 'atemp'. It's 0.83,
the last bit of that first malformed field. It is impossible in my
testing to make this line throw an I/O error.

I understand that the first field in my test case is malformed, that
it's really two numbers run together. What I'd hoped for was for the
i/o subsystem to throw an error so that I would be able to catch it in
my processing software. But since g77 doesn't see this field as
malformed, I can't. This is at odds with the f77 standard, in my
opinion (and also the opinion of Van Snyder here at JPL)



According to the F77 standard at 


http://www.fortran.com/fortran/F77_std/rjcnf0001-sh-13.html#sh-13.6

legitimate value separators are


   1. A comma optionally preceded by one or more contiguous blanks and
      optionally followed by one or more contiguous blanks

   2. A slash optionally preceded by one or more contiguous blanks and
      optionally followed by one or more contiguous blanks

   3. One or more contiguous blanks between two constants or following
      the last constant


My reading of that says that at the very least it should not have read
that one field into two values.



The particulars of my system are...

% g77 -v
Reading specs from /usr/lib/gcc/i386-redhat-linux/3.4.6/specs
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man 
                  --infodir=/usr/share/info --enable-shared 
                  --enable-threads=posix --disable-checking 
                  --with-system-zlib --enable-__cxa_atexit 
                  --disable-libunwind-exceptions --enable-java-awt=gtk 
                  --host=i386-redhat-linux
Thread model: posix
gcc version 3.4.6 20060404 (Red Hat 3.4.6-8)


% uname -a
Linux iguana.jpl.nasa.gov 2.6.9-55.0.2.plus.c4smp #1 SMP Fri Jul 6 05:25:07 EDT
2007 i686 i686 i386 GNU/Linux


William Daffer


-- 
           Summary: f77 reads one field into two variables in list directed
                    i/o
           Product: gcc
           Version: 3.4.6
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: William dot Daffer at jpl dot nasa dot gov


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33251

[Bug fortran/33251] f77 reads one field into two variables in list directed i/o

[burnus at gcc dot gnu dot org]

------- Comment #1 from burnus at gcc dot gnu dot org  2007-08-30 18:26 -------
I tried you example with g77 and it shows "No Error". However, using all other
compilers I have (ifort, sunf95, openf95, g95, gfortran, NAG f95) it shows
"Error!".

...

Ok, after re-reading your bug report, I see that you report a bug against g77
and not against gfortran (which is not affected).

g77 was part of GCC 3.4.x and is no longer supported.

gfortran is part of GCC since 4.0.0, supports Fortran 90/95 (and thus also
FORTRAN 77); it also supports Cray pointers and other legacy extensions and it
should support 99% of the extensions of g77. Plus it has better diagnostic
capabilities.

You should be able to get gfortran binaries (please use gfortran 4.1.x or
later) from your vendor (RedHat) or from:
http://gcc.gnu.org/wiki/GFortranBinaries#GNU/Linux

Closed as WONTFIX (with regards to g77), I could have also used WORKSFORME as
gfortran behaves properly.

Please use the fortran<At>gcc.gnu.org mailing list if you have further
questions.


-- 

burnus at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |WONTFIX


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33251

[Bug fortran/33251] f77 reads one field into two variables in list directed i/o

[William dot H dot Daffer at jpl dot nasa dot gov]

------- Comment #2 from William dot H dot Daffer at jpl dot nasa dot gov  2007-08-30 19:33 -------
Subject: Re:  f77 reads one field into two variables in
        list directed i/o

On Thu, 2007-08-30 at 18:26 +0000, burnus at gcc dot gnu dot org wrote:
> 
> ------- Comment #1 from burnus at gcc dot gnu dot org  2007-08-30 18:26 -------
> I tried you example with g77 and it shows "No Error". However, using all other
> compilers I have (ifort, sunf95, openf95, g95, gfortran, NAG f95) it shows
> "Error!".

Yes, that's what happened when we tried lahey and nag.


> 
> ...
> 
> Ok, after re-reading your bug report, I see that you report a bug against g77
> and not against gfortran (which is not affected).
> 
> g77 was part of GCC 3.4.x and is no longer supported.
> 

Okay.

> gfortran is part of GCC since 4.0.0, supports Fortran 90/95 (and thus also
> FORTRAN 77); it also supports Cray pointers and other legacy extensions and it
> should support 99% of the extensions of g77. Plus it has better diagnostic
> capabilities.

Okay. I'll see whether we can use that. 

thanks for the quick response!

William


> 
> You should be able to get gfortran binaries (please use gfortran 4.1.x or
> later) from your vendor (RedHat) or from:
> http://gcc.gnu.org/wiki/GFortranBinaries#GNU/Linux
> 
> Closed as WONTFIX (with regards to g77), I could have also used WORKSFORME as
> gfortran behaves properly.
> 
> Please use the fortran<At>gcc.gnu.org mailing list if you have further
> questions.
> 
> 


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33251