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From: mikeb@copper.UUCP (Mike Beckerman)
Newsgroups: net.lang.c
Subject: Re: for != while
Message-ID: <570@copper.UUCP>
Date: Wed, 3-Sep-86 11:25:08 EDT
Article-I.D.: copper.570
Posted: Wed Sep  3 11:25:08 1986
Date-Received: Thu, 4-Sep-86 21:42:17 EDT
References: <86900030@haddock> <15525@ucbvax.BERKELEY.EDU>
Reply-To: mikeb@copper.UUCP (Mike Beckerman)
Organization: Tektronix, Inc., Beaverton, OR.
Lines: 37

In article <15525@ucbvax.BERKELEY.EDU> ballou@brahms.UUCP (Kenneth R. Ballou) writes:
>In article <86900030@haddock> karl@haddock writes:
>>
>>It's well known that the equivalence between for and while breaks down if
>>there's a "continue" statement.  Here's another case I just discovered:
>>
>>main() {
>>	char *foo = "outer";
>>	for (;; printf(foo),exit(0)) {
>>		char *foo = "inner";
>>	}
>>}
>>
>>This prints "outer" (vax SVR2 compiler), though the for-while equivalence
>>might lead one to expect "inner".
>
>I don't think the issue here is equivalence of for and while statements.
>The point is that the scope of the inner 'foo' is the compound statement
>which is the body of the for statement.  So, quite rightly, the 'foo'
>given as the argument to printf in the third expression of the for statement
>refers to the most closely nested declaration of 'foo' -- the body of the
>for statement is one block level higher and is not visible at this point.

That was my first thought as well, but both K&R and the proposed ANSI C standard
define the "for" loop as follows:

	for (expression-1 ; expression-2 ; expression-3) statement

		is equivalent to

	expression-1;
	while (expression-2) {
		statement
		expression-3;
	}

which to me says that the example should have printed "inner".