User Changes Trunk

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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

Implementation Changes

Property field access lists no longer allows classes

  • Old behaviour: A field access list for a property is allowed to contain implicit dereferences in the form of fields of class instances.
  • New behaviour: A field access list for a property must only contain record or (TP style) object fields.
  • Reason:
    • Delphi compatibility
    • This resulted in an internal error for published properties
  • Remedy:
    • Switch the fields to records or objects
    • Use a method with inline modifier that will result in similar performance
  • svn: 40656
  • Example: The following code now fails:
unit Test;
{$mode objfpc}


  TTest1 = class
    Field: String;

  TTest2 = class
    fTest1: TTest1;
    property Prop: String read fTest1.Field; // Error "Record or object type expected"



Disabled default support for automatic conversions of regular arrays to dynamic arrays

  • Old behaviour: In FPC and ObjFPC modes, by default the compiler could automatically convert a regular array to a dynamic array.
  • New behaviour: By default, the compiler no longer automatically converts regular arrays to dynamic arrays in any syntax mode.
  • Reason: When passing a dynamic array by value, modifications to its contents by the callee are also visible on the caller side. However, if an array is implicitly converted to a dynamic array, the result is a temporary value and hence changes are lost. This issue came up when adding TStream.Read() overloads.
  • Remedy: Either change the code so it no longer assigns regular arrays to dynamic arrays, or add {$modeswitch arraytodynarray} a
  • Example: this program demonstrates the issue that appeared with the TStream.Read() overloads that were added (originally, only the the version with the untyped variable existed)
{$mode objfpc}
  tdynarray = array of byte;

procedure test(var arr); overload;

procedure test(arr: tdynarray); overload;

  regulararray: array[1..1] of byte;
  writeln(arr[0]); // writes 0, because it calls test(tdynarr)
  • svn: 42118

Range checking for enumeration constants in Delphi mode

  • Old behaviour: Out-of-range enumeration constants never caused an error in Delphi mode, because very early versions of Delphi did not either.
  • New behaviour: Out-of-range enumeration constants cause an error in Delphi mode, even if range checking is disabled. Current Delphi versions (and even older ones, such as Delphi 7) behave the same.
  • Reason: Delphi-compatibility.
  • Remedy: Fix the range errors.
  • svn: 42272, 42275

Directive clause […] no longer useable with modeswitch PrefixedAttributes

  • Old behaviour: A function/procedure/method or procedure/method variable type could be followed by a directive clause in square brackets ([…]) that contains the directives for the routine or type (e.g. calling convention).
  • New behaviour: If the modeswitch PrefixedAttributes is enabled (which is the default in modes Delphi and DelphiUnicode) the directive clause in square brackets is no longer allowed.
  • Reason: As custom attributes are bound to a type/property in a way that looks ambiguous to a directive clause and this ambiguity is not easily solved in the parser it is better to disable this feature.
  • Remedy:
    • don't set (in non-Delphi modes) or disable modeswitch PrefixedAttributes (in Delphi modes) if you don't use attributes ({$modeswitch PrefixedAttributes-})
    • rework your directive clause:
// this
procedure Test; cdecl; [public,alias:'foo']

// becomes this
procedure Test; cdecl; public; alias:'foo';
  • svn: 42402

Unit changes

System - TVariantManager

  • Old behaviour: TVariantManager.olevarfromint has a source parameter of type LongInt.
  • New behaviour: TVariantManager.olevarfromint has a source parameter of type Int64.
  • Reason for change: 64-bit values couldn't be correctly converted to an OleVariant.
  • Remedy: If you implemented your own variant manager then adjust the method signature and handle the range parameter accordingly.
  • svn: 41570

64-bit values in OleVariant

  • Old behaviour: If a 64-bit value (Int64, QWord) is assigned to an OleVariant its type is varInteger and only the lower 32-bit are available.
  • New behaviour: If a 64-bit value (Int64, QWord) is assigned to an OleVariant its type is either varInt64 or varQWord depending on the input type.
  • Reason for change: 64-bit values weren't correctly represented. This change is also Delphi compatible.
  • Remedy: Ensure that you handle 64-bit values correctly when using OleVariant.
  • svn: 41571

Classes TCollection.Move

  • Old behaviour: If a TCollection.Descendant called Move() this would invoke System.Move.
  • New behaviour: If a TCollection.Descendant called Move() this invokes TCollection.Move.
  • Reason for change: New feature in TCollection: move, for consistency with other classes.
  • Remedy: prepend the Move() call with the system unit name: System.move().
  • svn: 41795

Previous release notes