User Changes Trunk

About this page

Listed below are intentional changes made to the FPC compiler (trunk) since the previous release that may break existing code. The list includes reasons why these changes have been implemented, and suggestions for how you might adapt your code if you find that previously working code has been adversely affected by these recent changes.

The list of new features that do not break existing code can be found here.

Please add revision numbers to the entries from now on. This facilitates moving merged items to the user changes of a release.

All systems

Language Changes

Visibility of generic type parameters

• Old behaviour: Type parameters of generics had public visibility.
• New behaviour: Type parameters of generics now have strict private visibility.
• Reason: With the previous visibility it was possible to create code that leads to infinite loops during compilation or other hard to debug errors. In addition there is no real possibility to work around this issue (for an example see this bug report). Also the fix is Delphi compatible.
• Remedy: Declare a type alias for the type parameter with the desired visibility.
• Example: In the following example T is declared as strict private, while TAlias is declared as public and thus can be used as before the change.

type
  generic TTest<T> = class
  public type
    TAlias = T;
  end;

Parsing of specialize is changed

• Old behaviour: specialize was used to initialize a specialization and was followed by a type name that might contain a unit name and parent types.
• New behaviour: specialize is now considered part of the specialized type, just as generic is. This means that unit names and parent types need to be used before the part containing the specialize.
• Reason: This allows for a more logical usage of specialize in context with nested types (especially if multiple specializations are involved) and more importantly generic functions and methods.
• Remedy: Put the specialize directly in front of the type which needs to be specialized.