Order of evaluation of post-increment operator

[John Colvin via Digitalmars-d-learn]

On Sunday, 28 December 2014 at 20:25:59 UTC, bearophile wrote:
> John Colvin:
>
>> I guess there are cases where it's not easily catchable:
>>
>> void foo(int* p0, int* p1)
>> {
>>    (*p0)++ = (*p1)++;
>> }
>>
>> what happens when p0 == p1?
>
> The undefined code can be found statically, the run-time values 
> are irrelevant.
>
> Bye,
> bearophile

It depends what you mean by "undefined". Sure, the order of those 
2 ++ operations is undefined in all cases, but it doesn't lead to 
undefined *behaviour* unless the pointers are the same.

There's loads of code out there that has undefined order of 
operations but is invariant w.r.t. said ordering and is therefore 
correct.