confusing code....whats the point of this construct ?

[Bjørn Mork]

Valdis.Kletnieks at vt.edu writes:
> On Wed, 11 Mar 2015 18:37:32 -0000, Jeff Haran said:
>
>> I don't understand the problem here. The caller passes in a condition to be
>> evaluated in a loop. Many times that condition is quite simple (e.g. a counter
>> being non-zero). If it was a function the caller would have to pass in a
>> pointer to a function that does the evaluation, as in:
>
> We do pointers to callback functions all the time.  We try *really* hard
> to avoid anonymous lambda functions (which is basically what we have here).
>
> The problem here is that there's about 3 zillion ways to screw up the inline
> version, starting with the compiler optimizing the control variable into a
> hoisted load outside the loop and causing the test to always fail - note that
> the macro does *not* use any barriers or volatile or anything like that.

We could go a couple of more rounds on this, but I don't think there is
much point.  It is sufficent to note that there are different views on
the subject.  None of them are "right" or "wrong". Use a function if you
like. There are probably 3 zillion ways to screw up either way :-)


Bjørn