Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!rice!katzo.rice.edu!zdenko
From: zdenko@katzo.rice.edu (zdenko tomasic)
Newsgroups: comp.sys.mips
Subject: Re: f77 compiler bug (both MIPS and SGI)
Summary: a program bug, not compiler one
Message-ID: <1991Jun17.224729.15190@rice.edu>
Date: 17 Jun 91 22:47:29 GMT
References: <1991Jun17.174155.13484@cpsc.ucalgary.ca>
Sender: news@rice.edu (News)
Organization: Rice University
Lines: 58

In article <1991Jun17.174155.13484@cpsc.ucalgary.ca> cliff@phys.ucalgary.ca writes:
>I've discovered an interesting 'glitch' in the f77 compiler for
>MIPS (and consequently, for SGI, also). given a code skeleton of :
>
>   if (...) goto 10
                  ^^  jump into the body of the loop from outside!
                     (the continue statement is a part of the loop)
>      .
>      .
>      .
>   do 10 ....
>      .
>      .
>      .
>10 continue
 ^^
This jump is illegal fortran, so anything can happen at the execution time.



>
>From the above, if the 'if' evaluates to TRUE, then the following code,
>including the DO loop are supposed to be skipped.  This doesn't happen
>under MIPS-fortran.  Instead, the loop-code is executed using a value
>of "whatever" for the control loop variable.  Now (personally) I don't
>see that as a compiler bug, more a case of antequated coding style.
>(ie. the purpose of the '10 continue' becomes ambigous).  Anyway, I thought
>I would post this in case others are suffering program failures for the
>same or similiar reason.  BTW : the fix to the above is of the form :
>
>
>    if (...) goto 11
>       .
>       .
>       .
>    do 10 ....
>       .
>       .
>       .
> 10 continue
> 11 continue
>
      The above is most likely the proper fix for the program bug.

>ttfn
>
>-- 
>Cliff Marcellus                       |  Internet : cliff@phys.ucalgary.ca
>Department of Physics and Astronomy   |  SPAN     : CANCAL::CLIFF
>The University of Calgary
>OPINIONS EXPRESSED WITHIN ARE MY OWN AND NOT THOSE OF THE UNIVERSITY OF CALGARY


--
___________________________________________________________________
Zdenko Tomasic, Rice U., Chem. Dept., P.O. Box 1892, Houston, Tx 77251
INTERNET: zdenko@katzo.rice.edu
___________________________________________________________________