conditional expression evaluation question

[Mike McNally]

My small contribution to this silly topic:

    x = (*cp++ | *cp++ | *cp++);                                (1)
    if (x) ... /* or !x or whatever */

In computing the value to be assigned to the variable `x', the compiler
cannot short-circuit the expression.  This should be clear; in the
simpler case

    x = (a | b | c);

if the variable `a' contains zero, the compiler must still OR the
contents of `b' and `c' to determine the result.  These are bitwise
logical operators.  Short-circuiting these makes no more sense than
short-circuiting a sequence of multiplies as soon as one of the
operands evaluates to `1'.

I of course agree that a potential problem exists with (1) above.  If
the evaluation of `*cp++' is not atomic, and the increment could be
delayed, the result may be equal to the first byte of the series.  In
any case, `cp' must be incremented by `3' and both bitwise-OR operations
must be performed.  Oh well, I guess an optimizing compiler that 
delays the increments might realize this and skip the OR's...this
is getting ridiculous.

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Mike McNally                                    Digital Lynx Inc.
Software (not hardware) Person                  Dallas  TX  75243
uucp: {texsun,killer,infotel}!pollux!bobkat!m5  (214) 238-7474