[fpc-pascal] Question: range checking for string indexing

[Vinzent Höfler]

Tom Verhoeff wrote:

> On Wed, Oct 29, 2008 at 09:58:10PM +0100, Vinzent Höfler wrote:
>> Tom Verhoeff wrote:
>>
>>> I am surprised that for ShortString, the range is not
>>> also 1 <= i <= Length(s).
>>>
>>> IIRC Turbo Pascal only allowed you to access s[0] when range checking
>>> was off, and similarly for s[i] with i > Length(s).
>> No. See transcript:
> 
> That looks rather convincing.
> 
>> Borland Pascal  Version 7.0  Copyright (c) 1983,92 Borland International
> 
> However, IIRC there were some differences between Borland Pascal
> and Turbo Pascal (as it was named before they marketed it as
> Borland Pascal).

Yes, there were. But regarding string handling, nothing changed, at 
least not between TP5.5 and BP7. And I know for sure that accessing 
element 0 was always allowed, because it could be taken as shortcut for 
reading or even changing the length.

> Nevertheless, this means that AnsiStrings and ShortStrings are slightly
> more different than suggested in the documentation.

Well, if you put it this way, yes. With ShortStrings you rather get a 
maximum size (where indexing is allowed regardless of the actual length, 
although the behaviour could be considered more or less undefined - just 
like accessing uninitialized memory), whilst AnsiString's behaviour 
doesn't distinguish between length and (maximum) size.


Vinzent.