[fpc-pascal] Move with pointers to memory

[Frederic Da Vitoria]

2013/11/13 Sven Barth <pascaldragon at googlemail.com>

>  Am 13.11.2013 11:07, schrieb Frederic Da Vitoria:
>
>  2013/11/13 Rainer Stratmann <rainerstratmann at t-online.de>
>
>>  On Wednesday 13 November 2013 10:52:23 you wrote:
>> > 2013/11/13 Rainer Stratmann <rainerstratmann at t-online.de>
>> > > Is there a description of the behaviour of const and var in this case?
>> > > Why is it not both const or both var?
>> >
>> > "source" is where the data "comes from", so the procedure won't modify
>> it
>> > (if there is no memory overlap between source and dest), so it is
>> declared
>> > as "const"
>> > "dest" is where the data is copied to, so the procedure will necessarily
>> > modify it (if "count" is <> 0), and the procedure should modify so it is
>> > declared as "var". Actually, IMO it could be declared as "out", this
>> would
>> > avoid a meaningless warning.
>>
>>  But why does it work without specifying the vars more exactly like in
>> other
>> cases?
>>
>
>  You mean, how can it work without using typed variables? In Pascal, you
> don't have to give the type of a parameter, although 99.99% of the times
> you should do it. If you don't do it, you could as well use assembly :-)
> Actually, that's probably how Move is written: in assembly language. Of
> course, since the types were not given in the parameter declaration of
> Move, the compiler can't know the size of the data, and you have to give
> the compiler some indication. That's what "count" is for. Move considers
> the memory as 2 big arrays of bytes, one starting at "source", and the
> second at "dest".
>
> The fallback implementation (for new architectures) is written in Pascal.
> See $fpcdir\rtl\inc\generic.inc.
>

Of course it is, I should have guessed it, Lazarus/FPC is multi-platform. I
keep thinking as if I was using a Windows-only development tool.

-- 
Frederic Da Vitoria
(davitof)

Membre de l'April - « promouvoir et défendre le logiciel libre » -
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