Re: Unchecked_Deallocation with tagged types

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 2021-04-18 12:20, J-P. Rosen wrote:
> Le 18/04/2021 à 11:09, Jeffrey R. Carter a écrit :
>> On 4/18/21 10:46 AM, Gautier write-only address wrote:
>>> Side note: did anyone already suggest a new keyword: unchecked_free 
>>> and a special statement:
>>>
>>>    unchecked_free Some_Pointer;
>>
>> For every access variable P, there could exist the attribute procedure
>>
>>    P'Free;
>>
> Which would defeat the goal of Unchecked_Deallocation.
> 
> Ada (or more precisely Ichbiah) chose to deallocate through an 
> instantiation of a generic for good reason. Deallocation is a place 
> where many problems can come from, it is important to be able to trace 
> where they are. The current solution forces you to put "with 
> Unchecked_Deallocation" on top of every module that deallocates, 
> therefore telling the reader that there is some danger in it, and making 
> it easier to find where all the deallocations happen.

No, that does not work. If we supposed to search for all calls to 
deallocate, then attribute 'Free is much easier to look after than first 
looking for "with Unchecked_Deallocation", then for an instantiation of 
it with the types in question and then for the name of the instance.

> Now, I know that in those days, ease of writing is considered more 
> important than ease of reading and long term maintenance...

Yes, but dangling pointers is a more complex problem, that effortlessly 
passes brief code inspections. I agree with you in general, but disagree 
in this case. *IF* pointers are used *THEN* Unchecked_Deallocation only 
obfuscates things rather than helps.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de