On Thu, 5 Oct 2006, Jinesh K J wrote:
But, let us clear things up before leaving the topic off. With
reference to ISO/IEC 9899:1999(E), the following could be observed:
...
- value of a void expression shall not be used in any way
- If an expression of any other type(which included our variable 'a')
is evaluated as a void expression, its value or designator is
discarded.
- Here there are no side effects( no function call, assignments, etc)
I hope my observations are correct.
You may be right. Reading standards is hairy and I would also consider the
interpretation "evaluate the expression and discard the value" valid.
Although I'm nitpicking here, say if foo were a hardware register which
had a side effect of some sorts when reading it, then the statement *foo;
would actually do something even though the value wouldn't be used (better
declare foo volatile too to make sure the compiler doesn't optimize it
away).
In any case, I wouldn't like to let a line like
*( (char *) 0);
pass by the compiler, whether or not the actual compiler conforms to the
standard, whichever the interpretation of the standard may be. It's one of
the situations that I would imagine a compiler designer could get wrong,
regardless what the standard says...
/Ricard
--
Ricard Wolf Wanderlöf ricardw(at)axis.com
Axis Communications AB, Lund, Sweden www.axis.com
Phone +46 46 272 2016 Fax +46 46 13 61 30
