2015-12-16 11:55 GMT+01:00 Jonas Maebe <jonas.ma...@elis.ugent.be>:
>
> Santiago A. wrote on Wed, 16 Dec 2015:
>
> In functions blockread and blockwrite, the result parameter is "var".
>> And in blockread buffer is also "var".
>>
>> Couldn't they be marked as "out" instead of "var"?.
>>
>
> The result parameters can be changed. The BlockRead buffer parameter
> cannot be changed for the same reason that the parameters of fillchar and
> move cannot be changed: it changes the behaviour in case a managed type, or
> e.g. a record or array containing managed types, it passed. With "var",
> nothing special happens, while with "out", they are first finalised. If
> they are not yet initialised at that point (e.g. because they are the
> result of a plain getmem), this would introduce crashes.
>
> Even though you cannot just blockread/blockwrite managed types anyway
> (since they are pointers), this can currently work if you ensure that all
> read/written managed types are nil. It may seem unlikely, but at least
> changing the "var" parameters of move/fillchar to "out" even caused crashes
> in the compiler because the RTL relies on the current behaviour (and using
> move/fillchar with managed types is not very common/recommended either in
> the general case).
>
Thank you Jonas for this answer. This has been frustrating me, at least now
I have an idea why.
Now what I should do is add {%H-} on each line containing blockread,
blockwrite, fillchar and so on... This isn't so difficult, after all. The
only drawback is that it could potentially hide another perfectly valid
warning.
--
Frederic Da Vitoria
(davitof)
Membre de l'April - « promouvoir et défendre le logiciel libre » -
http://www.april.org
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