Incompatible types: 'PAnsiChar' and 'PWideChar'

Question

I am very new in delphi XE8. I have this following code which is from my delphi version 6 and I want to run it in delphi XE8.

1. function UTF8ToStringLen(const src: PChar; const Len: Cardinal): widestring;
2. var
3.   l: Integer;
4. begin
5.   SetLength(Result, Len);
6.   if Len > 0 then
7.   begin                                             
8.     l := MultiByteToWideChar( CP_UTF8, 0, src, Len, PWChar(Result), Len*SizeOf(WideChar));  <--error
9.     SetLength(Result, l);
10.   end;
11. end;
12. 
13. 
14. function StringToUTF8Len(const src: PChar; const Len: Cardinal): string;
15. var
16.   bsiz: Integer;
17.   Temp: string;
18. begin
19.   bsiz := Len * 3;
20.   SetLength(Temp, bsiz);
21.   if bsiz > 0 then
22.   begin
23.     StringToWideChar(src, PWideChar(Temp), bsiz);
24.     SetLength(Result, bsiz);                
25.     bsiz := WideCharToMultiByte(CP_UTF8, 0, PWideChar(Temp), -1, PChar(Result), bsiz, nil, nil);  <--error
26.     if bsiz > 0 then dec(bsiz);
27.     SetLength(Result, bsiz);
28.   end;
29. end;

when I try to run it the error points to line 8 and 25 in the code with an error message saying

ERROR MESSAGE: Incompatible types: 'PAnsiChar' and 'PWideChar'

I have search everywhere for the solution but I just cant solve the problem. Please help.. Thank you.

Answer 1

In Delphi 2007 and earlier, PChar is an alias for PAnsiChar. In Delphi 2009 and later, PChar is an alias for PWideChar. So by changing compiler you change the meaning of the code.

You can resolve this simply by replacing PChar with PAnsiChar and the code will have its original meaning.

In modern Unicode Delphi it would be more natural to use string (alias of UnicodeString) instead of the COM WideString. You might also use of one the many library routines to perform UTF-8 conversion.

There are surely going to be other issues ahead of you. I recommend that you read Marco Cantù's whitepaper on Unicode in Delphi as your next move.