DIP77 - Fix unsafe RC pass by 'ref'

[Walter Bright via Digitalmars-d]

On 4/11/2015 2:18 AM, "Marc =?UTF-8?B?U2Now7x0eiI=?= <schuetzm at gmx.net>" wrote:
> On Friday, 10 April 2015 at 21:26:14 UTC, Walter Bright wrote:
>> On 4/10/2015 11:28 AM, "Marc =?UTF-8?B?U2Now7x0eiI=?= <schuetzm at gmx.net>" wrote:
>>> Example:
>>>
>>> void foo() @safe {
>>>     RCArray!int arr = [0,1,2];
>>>     {
>>>         int* p = &arr[0];  // legal under new scope rules
>>
>> This would be a bad design of an RCO. RCO's must be constructed to not allow
>> pointers to the payload other than by ref.
>
> There is no reason for this restriction.

The reason is to prevent unsafe access of the payload.


> But if this is your opinion, why did
> you agree to "implement 'scope' and 'return' for arrays, classes, and pointers"?
>
> http://forum.dlang.org/post/mfhkbm$2vbk$1@digitalmars.com
>
> It makes no sense to implement that, but not allow it to be used safely.

In your example posted upthread, it wasn't safe. Perhaps scoped pointers can't 
be made safe for RCOs, or perhaps the proposal needs more thinking. I don't know 
at the moment.