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From: langer@gibbs.uchicago.edu (Steve Langer)
Newsgroups: comp.lang.c
Subject: what is this supposed to do?
Keywords: left shift
Message-ID: <1991Apr22.225641.1122@midway.uchicago.edu>
Date: 22 Apr 91 22:56:41 GMT
Sender: news@midway.uchicago.edu (NewsMistress)
Reply-To: langer@control.uchicago.edu (Steve Langer)
Organization: The James Franck Institute - The University of Chicago
Lines: 32

Hi -- 
What is the expected output from the following program? Is it defined?

#include <stdio.h>

main() {
   printf("1 << 32 = %o\n", ((unsigned) 1) << 32);
}

Running on a Sun 4 gives 1.
Running on a Sun 3 gives 0.
Running on an Iris gives 1.

K&R (first edition) page 45 says that left shifts fill vacated bits by
0, which does not seem to be happening.

If the shift is done one step at a time the answer is 0 on the Sun 4 and
the Iris, as expected.

#include <stdio.h>

main() {
   int i;
   unsigned x = 1;
   for(i=0; i<32; i++) x <<= 1;
   printf("%o\n", x);
}

E-mail responses are welcome!
    Thanks in advance,
                   Steve
                   langer@control.uchicago.edu