Path: utzoo!attcan!uunet!lll-winken!ames!mailrus!iuvax!purdue!bu-cs!buengc!bph
From: bph@buengc.BU.EDU (Blair P. Houghton)
Newsgroups: comp.lang.c
Subject: Broken compilers? (was Re: Comma Operator)
Message-ID: <1904@buengc.BU.EDU>
Date: 14 Jan 89 19:31:39 GMT
References: <922@quintus.UUCP>
Reply-To: bph@buengc.bu.edu (Blair P. Houghton)
Followup-To: comp.lang.c
Organization: Boston Univ. Col. of Eng.
Lines: 33

In article <922@quintus.UUCP> nair@quintus () writes:
>What should this print?
>
>	int x, y;
>	printf("%d %d %d\n", (x = 1, y = 2), x, y);

I've emailed the conforming answer.  (I fixed the obvious typo, too).
Now, on to controversy.

A while back, someone indicated that they knew of a compiler optimizer
that would reduce something such as the above (ostensibly through
constant-reduction) to

printf("%d %d %d\n", (1,2), x, y);

or maybe even

printf("%d %d %d\n", 2, x, y);

So, you compiler-writing C-programmers, is this thing broken or what?

I mean, the assignment itself is not an expression per se, but a statement,
and comma operators deal in expressions.  But then, the assignment operators
are operators, and in this case hold a place up there with functions in
that they are expressions that can become statements with just the
concatenation of a semicolon.  It's in the syntax description.

So, "broken?"  "Not Broken?"  "Not worth the display phosphorescence
energy?"  What?

				--Blair
				  "I'm broke, too, but that's not
				   in the syntax description..."