On 29/05/12 16:20, Michel Fortin wrote:
On 2012-05-29 13:29:35 +0000, Don Clugston <d...@nospam.com> said:
On 27/05/12 02:45, Walter Bright wrote:
You could implement it as simply comparing the addresses - you'd be no
worse off than C is, and you would get the correct answer for pointers
both in and out of the array without needing special cases.
I think that's a no-go.
Implementation-specific behaviour at runtime is bad enough, but at
compile time, it's truly horrible. Consider that any change to
unrelated code can change the results. Something that makes it really
terrible is that the same function can be called in CTFE once before
inlining, and once after. Good luck tracking that down.
And at runtime, you have a debugger.
Wouldn't it be possible to just catch the case where you compare two
pointers not assigned from the same memory block and issue an error?
Here's an idea: make each CTFE pointer some kind of struct with a
pointer to the memory block and an offset. When comparing, if the memory
block isn't the same, it's an error. If you add or subtract to a
pointer, it'll still belong to the same memory block but with a
different offset, thus it remains comparable. When dereferencing, you
can make sure the pointer still points inside the block, assuming the
block knows its length.
Thats _exactly_ what it does right now.
