array !is null fails
BCS at pathlink.com
Tue Feb 13 11:55:53 PST 2007
Frits van Bommel wrote:
> I'd argue that if you have an array with a non-zero length but null
> pointer, you've already messed up somewhere. It should have been checked
> at whatever place sliced the null pointer.
Yup. But then again asserts should be used to check stuff you otherwise
can't control (incoming arguments and returns from 3rd party code etc.)
I go by the assumption that if an assert *ever* trips then, by
definition, you have a bug (unless you are trying to trip it in a
unittest or something).
Conditions that might happen without bugs should be handled with exceptions.
> (The only way to obtain such
> an array would be either slicing a raw pointer or using pointer
> casts/unions to access memory as a different type than it actually is,
> And it'd get even worse if you take a non-empty slice from such an array
> that doesn't start at index 0. Then you have'd an array with non-zero
> length and non-null pointer that is nevertheless very much invalid, and
> without any way to detect it.
Maybe there should be a gc.IsValid(void) function that returns true if
the full length of the array is readable (or is GC allocated if the
first is to hard).
I wonder what it would take to make asserts do that check when given an
assert(c); // is c "good"?
> : That is, short of indexing it and detecting the segfault/access
> violation caused, or resorting to system-dependent checks like "is it in
> the first page of memory".
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