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From: ark@alice.UUCP
Newsgroups: comp.lang.c
Subject: Re: Comparing chars to constants
Message-ID: <7373@alice.UUCP>
Date: Sun, 18-Oct-87 15:34:06 EDT
Article-I.D.: alice.7373
Posted: Sun Oct 18 15:34:06 1987
Date-Received: Mon, 19-Oct-87 01:59:37 EDT
References: <4663@elroy.Jpl.Nasa.Gov>
Organization: AT&T Bell Laboratories, Liberty Corner NJ
Lines: 21

In article <4663@elroy.Jpl.Nasa.Gov>, david@elroy.UUCP writes:
> From 6.6 both sides are converted into ints, 0x80 stays the
> same but if p is equal to 0x80 it may always be sign extended on
> some machines depending on its character sign convientions.

(the original question had to do with the expression  c==0x80  where
 c is a character variable)

Chars are indeed extended to ints for comparison, and that
extension may or may not involve sign extension.  Saying

	c == (char) 0x80

may indeed be more portable, as one would hope 0x80 will be
converted to a char and then undergo the same sign exension
as c, but I wouldn't want to bet on the compiler getting it
right.  Instead, consider making c an unsigned char or casting it:

	((unsigned char) c) == 0x80

(the outer parentheses are there for clarity)