Boszormenyi Zoltan írta:
> Tom Lane írta:
>
>> Boszormenyi Zoltan <zb@cybertec.at> writes:
>>
>>
>>> for (; length > 0 && ptr[--length] == 0xff;);
>>>
>>>
>>
>>
>>> I suspect that GCC does the "--length" after checking
>>> "length > 0" and before checking the "ptr[...] == 0xff",
>>> but HP CC does it before checking "length > 0".
>>>
>>>
>> If it does, that is *unquestionably* a bug in HP's CC and should be
>> reported to them.
>>
>
> Is it *really* a bug? I recalled a comment from my C teacher
> in '92 or '93 about this exact issue, that the prefix/postfix
> increment/decrement operators are executed in the
> statement in an implementation-defined order, i.e. they
> can be freely reordered or placed anywhere in the
> expression, provided that the postfix operator's evaluation
>
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Above is the prefix case obviously...
> is earlier than the usage of the variable it's used on and
> evaluation is later than the variable usage in the postfix case.
> This means that their usage has to be minimized so the
> result is unambiguous.
--
Bible has answers for everything. Proof:
"But let your communication be, Yea, yea; Nay, nay: for whatsoever is more
than these cometh of evil." (Matthew 5:37) - basics of digital technology.
"May your kingdom come" - superficial description of plate tectonics
----------------------------------
Zoltán Böszörményi
Cybertec Schönig & Schönig GmbH
http://www.postgresql.at/
