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From: hirchert@uxe.cso.uiuc.edu.UUCP
Newsgroups: comp.lang.fortran
Subject: Re: "Interesting" error interpretation
Message-ID: <50500009@uxe.cso.uiuc.edu>
Date: Fri, 18-Sep-87 13:08:00 EDT
Article-I.D.: uxe.50500009
Posted: Fri Sep 18 13:08:00 1987
Date-Received: Sun, 20-Sep-87 14:16:58 EDT
References: <5117@jade.BERKELEY.EDU>
Lines: 39
Nf-ID: #R:jade.BERKELEY.EDU:5117:uxe.cso.uiuc.edu:50500009:000:1555
Nf-From: uxe.cso.uiuc.edu!hirchert    Sep 18 12:08:00 1987


/* Written 12:58 am  Sep 17, 1987 by lagache@violet.berkeley.edu in uxe.cso.uiuc.edu:comp.lang.fortran */
/* ---------- ""Interesting" error interpretation" ---------- */
...
      PROGRAM PRACT
      REAL NUM1,NUM2,SUM
      WRITE(*,*) 'Enter two numbers to be added to each other:'
      READ(*,*) NUM1, NUM2
    SUM = NUM1 + NUM2
      WRITE(*,*)
      WRITE(*,*) 'The sum of the two numbers is : ',SUM
      STOP
      END

%f77 practice.f
practice.f:
   MAIN pract:
Error on line 4 of practice.f: syntax error
Warning on line 9 of practice.f: local variable num2 never used
Warning on line 9 of practice.f: local variable read never used
                                                ^^^^
----------------------------------------------> ???? <---------
...
/* End of text from uxe.cso.uiuc.edu:comp.lang.fortran */
I don't know about f77 specifically, but a number of Fortran processors make
an initial scan of a statement to remove blanks and determine what kind of
statement it is and then do the parse based on that knowledge.  Since the
erroneous combination of the READ statement and the assignment statement has
an equal sign not contained in parentheses, the scan apparently decided that
the combined statement was an assignment statement, which made READ the
variable being assigned to.

It might be better if the compiler discarded symbol table information extracted
from statements that don't parse correctly, but this can't really be called a
bug.

Kurt W. Hirchert
National Center for Supercomputing Applications
University of Illinois