Reality drives me to write less clean code, sorry for mistakenly posting in D.announce

[Mike Parker]

Mike Parker wrote:
> Bill Baxter wrote:
>> Mike Parker wrote:
>>> davidl wrote:
>>>>
>>>> First practice:
>>>>
>>>> char[] text;
>>>> char* p;
>>>> char* end;
>>>>
>>>
>>> Pointer arithmetic in D is a no-no, unless you are using memory 
>>> allocated outside of the GC. 
>>
>> That's news to me.  There's nothing wrong with using pointers, it's 
>> just more verbose and error prone than foreach.
> 
> Of course there's nothing wrong with /using/ pointers, but pointer 
> arithmetic is one item in a list of 'Undefined Behavior' regarding 
> pointers to GC memory. See the page 
> http://www.digitalmars.com/d/garbage.html (section titled Pointers and 
> the Garbage Collector).
> 
> This isn't really an issue in the present since the current GC doesn't 
> move anything around, AFAIK. But it's still a bad habit to get into (or 
> a good one to get out of for people with C backgrounds) and doesn't do 
> much for future-proofing.

Hmm. I could have sworn I had read something explicitly saying that any 
pointer arithmetic was bad. Looking at it again, the only related items 
I see are the following:

"Do not add or subtract an offset to a pointer such that the result 
points outside of the bounds of the garbage collected object originally 
allocated."

and

"Do not use byte-by-byte memory copies to copy pointer values. This may 
result in intermediate conditions where there is not a valid pointer, 
and if the gc pauses the thread in such a condition, it can corrupt memory."

Maybe there was something about this in the NG before? Or maybe I 
interpreted the item above as ruling out the incrementing of pointers.