DIP1000: Scoped Pointers (Discussion)

[Walter Bright via Digitalmars-d]

On 8/11/2016 1:53 AM, John Colvin wrote:
> On Thursday, 11 August 2016 at 08:45:38 UTC, Walter Bright wrote:
>> On 8/11/2016 1:29 AM, John Colvin wrote:
>>> Can someone talk me through the lifetime algebra for the following?
>>>
>>> void foo()
>>> {
>>>     int a;
>>>     int** c;
>>>     void bar()
>>>     {
>>>         int* b = &a;  <= ok, b has a smaller lifetime than a
>>>         c = &b;    <= error, c has a larger lifetime than b
>>>     }
>>>     bar();
>>>     *c; //undefined behaviour
>>> }
>
> but according to this rule:
>
> "For an unrestricted pointer, visibility is dictated by the usual lexical scope
> rules. Lifetime, however is dictated by the lifetime of the data to which the
> pointer points to."
>
> b should have the same lifetime as a, no?

When b is assigned the address of a, then the contents of b, as accessible 
through b, have the lifetime of b.