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From: timc@copper.UUCP
Newsgroups: comp.lang.c
Subject: ANSI C awkward examples
Message-ID: <1470@copper.TEK.COM>
Date: Wed, 18-Nov-87 16:36:10 EST
Article-I.D.: copper.1470
Posted: Wed Nov 18 16:36:10 1987
Date-Received: Sat, 28-Nov-87 13:29:23 EST
Reply-To: timc@copper.UUCP (Tim Carver)
Organization: Tektronix, Inc., Beaverton, OR.
Lines: 32


I tried to post this a few days ago, and I don't think it got out.  My
apologies to anyone who gets this twice.

Fun things to know about ANSI C:

    1)  In ANSI C, the usual arithmetic conversions treat int expressions
        differently from long expressions, even when the sizes of int and
        long are the same.

            According to 3.2.1.5:
                unsigned int u = 4000000000;   /* Assume 32 bit int and long */

                (u + 1)  > 50 is true;  but
                (u + 1L) > 50 is false.

    2)  This code fragment is not portable in ANSI C:
            u_long = u_char_1 * u_char_2;

            According to 3.2.1.1, the multiply is to be:
                ((int) u_char_1) * ((int) u_char_2)

            instead of
                ((unsigned int) u_char_1) * ((unsigned int) u_char_2).

            For a typical 8086 implementation (32 bit long, 16 bit int)
            if u_char_1 and u_char_2 each contain 200, the unsigned long
            result in u_long is 4,294,941,760, instead of the correct
            40,000.

            Unfortunately, this is not due to some sort of typo.  ANSI is
            aware of this example.