What is the difference between WideChar and AnsiChar?

Question

I\'m upgrading some ancient (from 2003) Delphi code to Delphi Architect XE and I\'m running into a few problems. I am getting a number of errors where there are incompatibl

Answer 1

A couple years ago, the default character type in Delphi was changed from AnsiChar (single-byte variable representing an ANSI character) to WideChar (two-byte variable representing a UTF16 character.) The char type is now an alias to WideChar instead of AnsiChar, the string type is now an alias to UnicodeString (a UTF-16 Unicode version of Delphi's traditional string type) instead of AnsiString, and the PChar type is now an alias to PWideChar instead of PAnsiChar.

The compiler can take care of a lot of the conversions itself, but there are a few issues:

1. If you're using string-pointer types, such as PChar, you need to make sure your pointer is pointing to the right type of data, and the compiler can't always verify this.
2. If you're passing strings to var parameters, the variable type needs to be exactly the same. This can be more complicated now that you've got two string types to deal with.
3. If you're using string as a convenient byte-array buffer for holding arbitrary data instead of a variable that holds text, that won't work as a UnicodeString. Make sure those are declared as RawByteString as a workaround.
4. Anyplace you're dealing with string byte lengths, for example when reading or writing to/from a TStream, make sure your code isn't assuming that a char is one byte long.

Take a look at Delphi Unicode Migration for Mere Mortals for some more tricks and advice on how to get this to work. It's not as hard as it sounds, but it's not trivial either. Good luck!