Purity of alloca()

[BCS]

Hello bearophile,

> Is alloca() pure?
> 
> Given the same input alloca() generally returns different pointers, so
> it's not a pure function.
> 
> But the same is true for the ptr field when you allocate an array on
> the heap.
> 
> And the memory allocated by alloca() never escapes the function, so it
> looks more pure than normal heap allocation :-)
> 

As long as you don't pop the stack and do funky stuff with pointers. Vote++
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