Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!pasteur!ucbvax!TECHNION.BITNET!AER7101
From: AER7101@TECHNION.BITNET (Zvika Bar-Deroma)
Newsgroups: comp.lang.fortran
Subject: fortran problem
Message-ID: <8806111222.AA06982@jade.berkeley.edu>
Date: 11 Jun 88 12:22:56 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 81
X-Unparsable-Date: Sat, 11 Jun 88 15:19:59 IST


Hello,
I have some questions concerning a bug (or  as I call it, when it
bares the name of a big manufacturer, an undocumented feature..).
I ran the following program on several machines. There is "some problem"
with the program, as in the subroutine, an attempt is made to redefine
a constant.
Naively enough, I expected to get a reasonably clear message in English,
(not HEX location of unknown registers..), just as the following will:
* this produces "clear" message:
      PARAMETER ( I=5)
      I=1
      END
The message you get follows:
*ERR* EQ-02 line 2, column 7, cannot assign value to expression
(That's WATFOR77's compiler, one could think of something better like:
"trying to redefine a constant", which I saw somewhere, but even that's
good enough..).

Now try to run the following program. Do NOT allocate files (if possible
with your system) and check the following:
     1. On which unit it printed 'THIS SHOULD BE PRINTED ON UNIT 1' ?
     2. What is the value of I printed on the default output unit ?

      CALL TRY ( 1 )
      WRITE (1,*) 'THIS SHOULD BE PRINTED ON UNIT 1'
      I=1
      WRITE (*,*) ' I (SHOULD BE 1) = ',I
      STOP
      END

      SUBROUTINE TRY ( KUKU )
      KUKU = 8
      RETURN
      END

Following are the results of some compilers (refer to the questions):

    compiler/machine           unit #    I    comments
************************       ******    *    ********
IBM VS FORTRAN 2.2.0             8       1    OPT(2) causes I to be 8 ..

IBM VS FORTRAN 1.4.1             8       8

WATFOR77  2.5                    1       1

CDC/NOS FTN5                     8       1

CDC/ NOS/VE FORTRAN                            runtime err: "ACCESS VIOLATION"
                                               + HEX location
 (when run with full debug causes the cursor to point at the "KUKU=8"
  line, in addition to the ACCESS VIOLATION error msg. )

VAX/VMS FORTRAN                                runtime err: "ACCESS VIOLATION"
                                               + HEX location

WATFIV                                        err. msg.:
***ERROR*** SUBPROGRAM TRY   REDEFINES A CONSTANT, EXPRESSION, DO-PARAMETER OR
ASSIGNED GOTO INDEX ( ARGUMENT NUMBER   1)
PROGRAM WAS EXECUTING LINE  1 IN ROUTINE M/PROG WHEN TERMINATION OCCURED

Unfortunately, WATFIV is FORTRAN 4 ....

How does your compiler execute this program ?
Can anyone tell me if/what the ANSI standard "says" to such a situation?
How about the 8x draft ?

(Of course, my program is a small demonstration of a problem that can
be serious, as happened to a user here with a program a few thousand
statements long, producing inexplicable results).

Regards,

Zvika Bar-Deroma
dept. of Aeronautical eng.
Technion, Haifa, Israel

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