Re: Proposal: Auto-allocation of Indefinite Objects

[Yannick Moy <moy@adacore.com>]

Hi Stephen,

On Saturday, April 4, 2020 at 12:48:43 AM UTC+2, Stephen Davies wrote:
> Firstly, apologies if this has already been discussed or, 
> more likely, if it's a really stupid idea for some reason 
> that I haven't thought of. 

Actually, that's something more and more of us would like to see.

> My proposal is that it should (sometimes?) be possible to declare 
> objects of indefinite types such as String and have the compiler 
> automatically declare the space for them without the programmer 
> having to resort to access types. 

I agree with the goal.

> Benefits: 
> 
> 1. Easier, especially for newbies/students. 
> 2. Safer due to reduced use of access types. 
> 3. Remove the need to have definite and indefinite versions of generic units. 

I agree with 2 only if we can combine this with safe handling of aliasing. It would be terrible to have such a feature lead to unsafe code if you somehow copy the pointer. Also, for strings that's possibly not the only change needed. What you'd like really is to be able to reassign the string to some larger/smaller string, like you do when using Unbounded_String.

On 2020-04-04, Jeffrey R. Carter wrote:
>
> the ARG is aware of them and has chosen to take no action.
> That seems unlikely to change.

On the other hand, AdaCore has launched a project to collect/discuss ideas/suggestions/problems regarding the evolution of Ada and SPARK: https://github.com/AdaCore/ada-spark-rfcs
Feel free to open an Issue there on that topic.