[fpc-devel] Why: "Can't take the address of constant expressions" here?

[Mattias Gaertner]

On Wed, 11 Jan 2023 23:58:34 +0100
Bart via fpc-devel <fpc-devel at lists.freepascal.org> wrote:

> Given the following program (an excerpt form a test program for a
> bugreport about the fpwidestring unit):
> 
> ===
> program test;
> {$codepage utf8}
> {$mode objfpc}
> {$h+}
> 
> uses
>   FpWideString;
> 
> var
>   WSource: WideString = 'source';
>   USource: UnicodeString = 'source';
>   WDest: WideString = '' ;
>   UDest: UnicodeString = '';
>   ASource: AnsiString = 'source';
>   ADest: AnsiString = '';
>   P: array[0..99] of AnsiChar;
> 
> begin
>   with WideStringManager do
>   begin
>     writeln(1);
>     Wide2AnsiMoveProc(pwidechar(WSource),RawByteString(ADest),
> CP_UTF8, Length(WSource));
>     writeln(2);
>     Ansi2WideMoveProc(PChar(ASource), CP_UTF8, UDest,
> Length(ASource));   //<< test.lpr(24,53) Error: Can't take the address
> of constant expressions (caret behind UDest)
> end.

First of all, adding a 'end;" for the "with" compiles under Linux.
That's because widestring=unicodestring on Linux.

On Windows widestring is not a unicodestring and thus it can't be
passed to a var parameter. 

https://wiki.freepascal.org/Widestrings

Mattias