what is this supposed to do?

[Erik Naggum]

In article <1991Apr23.003314.5194 at zoo.toronto.edu>, Henry Spencer writes:
   In article <1991Apr22.225641.1122 at midway.uchicago.edu>, Steve Langer writes:
   >What is the expected output from the following program? Is it defined?
   >   printf("1 << 32 = %o\n", ((unsigned) 1) << 32);

   Assuming you're on a 32-bit machine, no, it is undefined.  Translation,
   expect different machines to do different things, some of them unpleasant.

In concrete terms:

(1) Some machines treat the shift as "modulo word-length", i.e. 1 <<
    32 => 1 << 0 => 1.
(2) Some machines treat the shift as an unsigned integer, and the
    result as "modulo 2**wordlength", i.e. 1 << 32 => 4294967296 => 0.
(3) Some machines do something else when the shift operand is larger
    than the applicable word-size, such as laugh at you.

--
[Erik Naggum]					     <enag at ifi.uio.no>
Naggum Software, Oslo, Norway			   <erik at naggum.uu.no>