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