CompareChar: invalid result

Repost from https://forum.lazarus.freepascal.org/index.php/topic,68984.0.html

CompareChar

https://www.freepascal.org/docs-html/rtl/system/comparechar.html

-1
    if buf1 and buf2 contain different characters in the first len positions, and the first such character is smaller in buf1 than the character at the same position in buf2. 
0
    if the first len characters in buf1 and buf2 are equal. 
1
    if buf1 and buf2 contain different characters in the first len positions, and the first such character is larger in buf1 than the character at the same position in buf2.`

This means the possible result values are -1, 0, and 1; while in practice, it behaves like CompareByte and returns the difference between the character values in the ASCII table.

var
   s, d: string;
begin
   s := 'testaxxx';
   d := 'testxxxx';
   writeln(CompareChar(s[1], d[1], length(s)));
end.

It prints -23, the difference between Ord('a') and Ord('x').

Actually implementation of CompareChar is to use CompareByte:

function CompareChar(Const buf1,buf2;len:SizeInt):SizeInt;
begin
   CompareChar:=CompareByte(buf1,buf2,len);
end;