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From: Devin Jeanpierre <jeanpierreda@gmail.com>
Date: Tue, 17 Dec 2013 19:12:00 -0800
Subject: Re: Experiences/guidance on teaching Python as a first programming language
To: Chris Angelico <rosuav@gmail.com>
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On Tue, Dec 17, 2013 at 7:01 PM, Chris Angelico <rosuav@gmail.com> wrote:
> On Wed, Dec 18, 2013 at 1:33 PM, Devin Jeanpierre
> <jeanpierreda@gmail.com> wrote:
>> Yes you do. Lifetimes are hard, because you need to malloc a lot, and
>> there is no defined lifetime for pointers -- they could last for just
>> the lifetime of a stack frame, or until the end of the program, or
>> anywhere in-between, and it's impossible to know for sure, and if you
>> get it wrong your program crashes. So there's all these conventions
>> you have to come up with like "borrowing" and "owning", but they
>> aren't compiler-enforced, so you still have to figure it out, and you
>> will get it wrong. Successors like C++ mitigate these issues with
>> destructors (allowing heap-allocated stuff to be tied to the lifetime
>> of a stack), and smart pointers and so on.
>
> Wrong. A pointer is a scalar value, usually some kind of integer, and
> its lifetime is the same as any other scalar.

The duration of a pointer's validity is far more interesting, and that
is why it is the primary meaning of the term "pointer lifetime". Also,
it's obviously what I meant.

>  Heap memory's lifetime
> is also very simple: it lasts until freed.

Sometimes simple things are hard to use correctly. I only said it was
hard, not complicated.

-- Devin