Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!haven!aplcen!osiris!consult
From: consult@osiris.UUCP (Unix Consultation Mailbox )
Newsgroups: comp.os.os9
Subject: Re: printf bug with C compiler...fatal runtime error!
Message-ID: <2820@osiris.UUCP>
Date: 31 Jan 89 20:25:23 GMT
References: <1223@mmm.UUCP> <1225@mmm.UUCP>
Reply-To: consult@osiris.UUCP (Unix Consultation Mailbox (Phil))
Distribution: usa
Organization: The Johns Hopkins Hospital, Information Systems
Lines: 35

In article <1225@mmm.UUCP> manning@mmm.UUCP (Arthur T. Manning) writes
about a "bug" in the Microware C library code for printf.  I have a
couple of comments.

First, why is this "bug" a problem?  Is the bit pattern created by
poking 0x6666 into the middle of (double) 123.45 a legitimate double?
I doubt it; if it were, I think this problem would have been fixed
long ago.  I've never dealt with Microware, but they seem to be more
considerate of their customers than any software company I've ever
known.  (For one thing, they are willing to ascribe intelligence to
their customers - most companies just plain can't do this so it must
say something for the quality of Microware's clientele. :-)

Do you really need to be able to poke random bit patterns into doubles?
If so, I'd hate to ever have to support your software.

If it isn't just for fun, are you really worried about it?  Common
sense would say that doing something unsupported results in
indeterminate behavior.  I'd say that printf (or _doprnt or whatever)
bombing when told to interpret garbage correctly is acceptable behavior.
(You can't tell me that it's not doing what it should if you can't tell
me what "should" is.)

I guess my conclusion is "so what"?  It's either a really serious bug
that should have been fixed years ago or a meaningless, trivial side-
effect of misuse of the C language.

In any case, even though I'm dubious that this problem is a genuine
one, I *am* curious about why a fault occurs.  I'd try to figure it out
myself but don't know what endiosity a 68k uses and don't have my Sun
anymore to try it and see.  (Btw, it works just fine on a Pyramid 9820,
though the results are meaningless...)


phil