Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!cica!ctrsol!ginosko!uunet!mcsun!sunic!tut!tukki!sakkinen
From: sakkinen@tukki.jyu.fi (Markku Sakkinen)
Newsgroups: comp.lang.fortran
Subject: Standard conformance
Message-ID: <1301@tukki.jyu.fi>
Date: 14 Sep 89 10:37:15 GMT
Reply-To: markku@jytko.jyu.fi (Markku Sakkinen)
          SAKKINEN@FINJYU.bitnet (alternative)
Organization: University of Jyvaskyla, Finland
Lines: 45

The Fortran-77 standard _was_ accepted 11 years ago,
so one would suppose that the compiler writers have already
taken notice. Well... take this very simple example of an
_incorrect_ Fortran programme:

      INTEGER I, J
      IF (I .LT. 100000) GOTO 2
      DO 9 I = 1, 10
2     J = I * I
      WRITE (6, 100) I, J
9     CONTINUE
100   FORMAT (2I12)
      END

It contains a GOTO into a DO loop, which is illegal in Fortran-77.
Furthermore, very trivial static analysis could detect that the GOTO
here cannot be legal even according to the "extended range" rules
of Fortran-66.

I just tried this kind of example once again with Digital's VAX/VMS
Fortran compiler, turning on all possible STANDARD and WARNING switches
(I should think). The result: it compiled without the slightest complaint.
Then I tried the same with Sun's Fortran 77 compiler (with the -ansi
option), and it behaved likewise.

Jumping into a DO loop can easily happen as a kind of clerical error,
especially when old code is reworked. It can also cause puzzling
run-time effects so that it is difficult to find the original error.
Therefore detecting this error at compile time is very useful:
compilers should do their job!

The above-mentioned omission also makes one pessimistic about
how long even the most Fortran-oriented computer vendors will take
to really implement any Fortran-8X (or 9X?) standard,
even if such a standard becomes official.

Note: it was years ago that I last had to work with Fortran;
I just took up an old pet peeve.

Markku Sakkinen
Department of Computer Science
University of Jyvaskyla (a's with umlauts)
Seminaarinkatu 15
SF-40100 Jyvaskyla (umlauts again)
Finland