[fpc-pascal] Illogical automatic dereferencing

[Jonas Maebe]

Florian Klaempfl wrote on Tue, 13 Oct 2009:

> Jonas Maebe schrieb:
>> I think that "all pointers can be indexed as arrays" can easily cause
>> accidentantal errors though. I can't find it anymore, but I remember
>> Pierre once fixed a bug in the compiler sources itself where someone
>> accidentally used move(pstring_var[1],...) instead of
>> move(pstring_var^[1],..). That at least was not a case of not
>> understanding how pointers work, but a simple case of a typo which
>> couldn't be caught anymore by the compiler due to this extension.
>
> What is the alternative?

Only allowing it for pchar/pwidechar, I guess. And/or printing a  
warning in case you are "indexing a pointer" to a type that is an  
indexed type itself, although I'm not sure how we could make it  
possible to disable this warning on a case-by-case basis using some  
kind of explicit syntax saying "yes, I want  
(pointer+(n-1)*sizeof(pointer))^, not pointer^[n]".

> Declare things like
>
> tchar = array[0..maxint] of char;
> pchar = ^tchar;
>
> ?
>
> Small typo, move(p,... instead of move(p^,... and things break as well

The point is that it creates an extra class of small typos that can't  
be caught by the compiler if you allow it for all types. At least TP  
(and previous versions of Delphi) only allowed this for  
pchar/pwidechar afaik, where this particular error cannot occur (p^[i]  
is not valid if p is a pchar).


Jonas

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