zero based String

Question

in system.sysutils.pas, in Rio they add this instruction:

var intPart: String;

... IntPart.Chars[length(IntPart)] in ['1','3','5','7','9'] ...

But as far as i know, s.Chars[xx] will be always zero-based string so doing IntPart.Chars[length(IntPart)] in ['1','3','5','7','9'] will always go out of the boundary ?

it's must not be written instead

... IntPart.Chars[length(IntPart)-1] in ['1','3','5','7','9'] ...

Or I miss something ?

Answer 1

But as far as i know, s.Chars[xx] will be always zero-based string

Yes, the TStringHelper routines are written to operate on strings as zero based, regardless of the compiler settings ({$ZEROBASEDSTRINGS ON/OFF}). See SysUtils.TStringHelper.Chars.

so doing IntPart.Chars[length(IntPart)] in ['1','3','5','7','9'] will always go out of the boundary ?

That is correct. It should have been Length(IntPart)-1.

Reported as: SysUtils.InternalTextToCurrency accesses a string out of bounds

Update: Fixed in Delphi 10.3.3 Rio.

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Furthermore, when range check is on, IntPart.Chars[length(IntPart)] should have raised an exception. This is also bug (in TStringHelpers.Chars).

Reported as: TStringHelper.Chars does not issue a range error when index is out of bounds