SetString does not work for Unicode string?

Question

I am using Delphi XE3, and with the following code:

function Test(): string;
var
  Buffer: array[0..5] of WideChar;
  BufferLen: Cardinal;
  TempStr: UnicodeString;
begin
  SetString(TempStr, PWideChar(@Buffer[0]), BufferLen / 2);
end;

I always get the following error:

[dcc32 Error] Translator.pas(148): E2008 Incompatible types

But I check Does SetString have two version for AnsiString and UnicodeString accordingly? and confirm there are two versions of SetString, why does not work for Unicode?

SetString works perfectly for UnicodeString but it takes an integer for the third arg and you passed a floating point value. I also wonder what that divide by two is meant to do. Normally you'd pass a length in that argument. Why would you want to be passing half the length? — David Heffernan, Aug 06 '23 at 06:50
My guess is that you are imagining that BufferLen contains the size, i.e. number of bytes. Well if that was so you'd use div 2 or div SizeOf(Char) or div SizeOf(Buffer[0]). But a variable named BufferLen should contain a length (element count) rather than a size (byte count). You get the length of an array using the Length function, which works with fixed length arrays also. — David Heffernan, Aug 06 '23 at 07:01
If you are using XE3 why would you tag the question delphi-xe2. Details matter and this inattention to details will likely hinder your programming too. — David Heffernan, Aug 06 '23 at 07:02
@DavidHeffernan, you are correct, the problem comes from the BufferLen / 2. I pay too much attention to the UnicodeString. After changing BufferLen / 2 to BufferLen div 2, the issue disappears. The reason I use delphi-xe2 instead, because there is no tag delphi-xe3 available. — alancc, Aug 06 '23 at 10:38
No 'delphi-xe3' tag available? As you can see from my edit, there certainly is one, and has been since XE3 was released. Just note that all 'delphi-...' tags are not shown when you type 'delphi', you may need to type the '-xe' also or even '-xe3'. — Tom Brunberg, Aug 06 '23 at 16:59
BufferLen div 2 may compile but it sounds like it's still a bug — David Heffernan, Aug 06 '23 at 17:24
You should learn the basic Delphi operators. You've confused floating point division `/` with integer division `div`. The result of `BufferLen / 2` with `BufferLen = 10` would be the floating point value `5.0`, and the result with `BufferLen = 15` would be `7.5`. Neither of those values is appropriate to provide as the third arg to `SetString`, which is an integer. — Ken White, Aug 08 '23 at 03:08

SetString does not work for Unicode string?

0 Answers0