🚀 go-pugleaf

In article <1996Apr3.140147.1@fermi.nsrl.rochester.edu>, skulski@fermi.nsrl.rochester.edu writes:
> In article <3183BF9F.13D9@iis.nsk.su>,
>  Alex Nedorya <ned@iis.nsk.su> writes:
>> skulski@fermi.nsrl.rochester.edu wrote:
>>> 
>>> Is the following legal Oberon-2;
>>> 
>>>         Object* = POINTER TO ObjectDesc;
>>>         ObjectDesc* = RECORD END;
>>> 
>>>         Array* = POINTER TO ARRAY OF Object;
>>> 
>>> It compiles OK under Linux V4-0.9. However, I was told of at least
>>> one compiler Oberon-2 which does not compile this. Is the above
>>> construct legal, or is the said compiler broken?
>>> 
>>> Pls note, that for example Kepler uses the following to represent
>>> objects:                StarTab = POINTER TO ARRAY OF LONGINT;
>>> with calls to SYSTEM.VAL to convert POINTERS to  LONGINTs.
>>> 
>>> So, there is a potential problem here which Josef wanted to avoid.
>>>
>>> Is the "POINTER TO ARRAY OF Object" good legal Oberon, or is it not?
>> 
>> It is a good legal Oberon, no doubt.
>> What can be wrong with POINTER TO ARRAY OF POINTER?
> 
>  I was told that some older implementations of GC had problems with 
> this. 
> 
>> 
>> I've checked (under XDS) POINTER TO ARRAY OF ObjectDesc, 
>   because SIZE(ObjectDesc) is zero and it can 
>> cause a problem (array which element is of zero size), 
>   but both cases work OK.
> 
> Well, the purpose of Array is not to be used with Objects as such, but 
> with extensions of Objects. I have implemented an indexable array 
> of arbitrary Objects this way. (As a self advertisement, let me remind
> that it is available from ftp://nuchem.nsrl.rochester.edu/pub/Oberon/Objects.
> It is a data-management library with recursive abstract Containers,
> whose concrete realisations are a List and the said array. The whole 
> thing has also a platform-independent storage and a few other features.)
> 
> Wojtek

As far as I know, the GC of Mac Oberon V4 & Ceres don't mark pointers in
arrays. But anyway, this is an implementation restriction, and your code is
legal Oberon.

Simi