I need to unsubscribe to this email... But there is no message at the bottom with instructions... Can you help? -----Original Message----- From: Paul Eggert [mailto:eggert@penguin.cs.ucla.edu] On Behalf Of Paul Eggert Sent: Tuesday, August 03, 2004 10:02 AM To: Clive D.W. Feather Cc: tz@lecserver.nci.nih.gov Subject: Re: asctime.c "Clive D.W. Feather" <clive@demon.net> writes:
Can you give me an example?
Sure. Here's an example taken from the code I happened to be looking at 30 seconds before reading your email. It's taken from GNU coreutils "od.c". I've paraphrased the code slightly to simplify it. enum size_spec { NO_SIZE, CHAR, SHORT, INT, LONG } ; enum size_spec integral_type_size[sizeof (long) + 1]; for (i = 0; i <= MAX_INTEGRAL_TYPE_SIZE; i++) integral_type_size[i] = NO_SIZE; integral_type_size[sizeof (char)] = CHAR; integral_type_size[sizeof (short)] = SHORT; integral_type_size[sizeof (int)] = INT; integral_type_size[sizeof (long)] = LONG; This code has undefined behavior if, for example, sizeof (long) is 4 and sizeof (int) is 8. The code in difftime.c is a bit more subtle than this, and now that I look at it more carefully it can't strictly be justified in terms of either C89 or C99 (though it is true on all platforms I know about). However, I'd say that the general principle that sizeof(int) <= sizeof(long) is hardwired into a lot of real-world code. If there aren't any real implementations with sizeof(long) < sizeof(int), then this is only of academic interest. Still, it's strange that this longstanding requirement would get removed from the standard. After all, it's a natural assumption.