Path: utzoo!attcan!uunet!lll-winken!ames!hc!lanl!jlg
From: jlg@lanl.gov (Jim Giles)
Newsgroups: comp.lang.fortran
Subject: Re: DO loops, anyone?
Message-ID: <10623@lanl.gov>
Date: 17 Mar 89 23:35:34 GMT
References: <1913@devsys.oakhill.UUCP>
Organization: Los Alamos National Laboratory
Lines: 36

From article <1913@devsys.oakhill.UUCP>, by steve@oakhill.UUCP (steve):
> [...]
> Unfortunately you can't save the unwashed masses from themselves.
> Not only can you not prevent them from doing this.  If you forbid
> it, they cry and want it.  If you want to sell compilers, this is
> something that must be supported.

      do 10 i=1,10
         print *,i
         if (i.gt.5) goto 10
         do 10 j=1,5
            print *,j
 10   continue

This program infinite loops on the Cray with CFT 1.14.  If this is
the behaviour that "must be supported" to sell compilers, I don't
want any part of it.  I consider this to be an _ERROR_ in the 
compiler and I'm reporting it to Cray as such.  To be fair, the CFT
compiler does issue a warning that the branch is illegal.

If a compiler wants to allow the above program it should at least
compile it to something useful.  The only "meaningful" interpretation
of the above I can think of is equivalent to the following:

      do 10a i=1,10
         print *,i
         if (i.gt.5) goto 10a
         do 10 j=1,5
            print *,j
 10      continue
 10a  continue

If a compiler doesn't issue a FATAL message, it should give the above
interpretation - nothing else is acceptable.  (Note, I used '10a' as
the label in the above example to make it clear that it is a compiler
generated label.)