Problem: Free Pascal is not properly initializing and finalizing an interface type resulting in code being invoked for a garbage pointer. The error is highlighted at the end.
Previously I filed a bug report on this issue and received feedback that the bug could not be reproduced, but it's hitting me me big time when building on 32-bit Linux (I been working on 64-bit Linux withe same same compiler source without these problems). I'd like to post some code and get feedback on how to fix this problem, if it is either something I am doing or a problem with the compiler.
I have an interface type, what I would call a managed type since the compiler ought to generate code to initialize and finalize its value, which is used to share 1 or more contiguous floats:
IDependencyProperty = interface
['{E021AD95-9985-48AB-B29F-8D25A7BBE10E}']
function GetCount: Integer;
function GetValue(Index: Integer): Float;
procedure SetValue(Value: Float; Index: Integer);
property Count: Integer read GetCount;
end;The interface is exposed by records TVec(n)Prop where n represents the count or available floats. These properties are used to share float vectors with animations/storyboards or other objects. Here is an the listing of TVec1Prop:
TVec1Prop = record
private
function GetValue: TVec1;
procedure SetValue(Value: TVec1);
function GetVec(Index: Integer): TVec1Prop;
procedure SetVec(Index: Integer; const Value: TVec1Prop);
public
class operator Implicit(const Value: TVec1): TVec1Prop;
class operator Implicit(const Value: TVec1Prop): TVec1;
class operator Negative(const A: TVec1Prop): TVec1;
class operator Positive(const A: TVec1Prop): TVec1;
class operator Equal(const A, B: TVec1Prop) : Boolean;
class operator NotEqual(const A, B: TVec1Prop): Boolean;
class operator GreaterThan(const A, B: TVec1Prop): Boolean;
class operator GreaterThanOrEqual(const A, B: TVec1Prop): Boolean;
class operator LessThan(const A, B: TVec1Prop): Boolean;
class operator LessThanOrEqual(const A, B: TVec1Prop): Boolean;
class operator Add(const A, B: TVec1Prop): TVec1;
class operator Subtract(const A, B: TVec1Prop): TVec1;
class operator Multiply(const A, B: TVec1Prop): TVec1;
class operator Divide(const A, B: TVec1Prop): TVec1;
procedure Link(OnChange: TDependencyChangeNotify = nil); overload;
procedure Link(Prop: IDependencyProperty; Index: LongInt); overload;
procedure Unlink;
function Linked: Boolean;
function Equals(const A: TVec1Prop): Boolean;
function Same(const A: TVec1Prop): Boolean;
property X: TVec1Prop index 0 read GetVec write SetVec;
property Value: TVec1 read GetValue write SetValue;
property Vec[Index: Integer]: TVec1Prop read GetVec write SetVec;
private
FProp: IDependencyProperty;
case Boolean of
True: (FIndex: LongInt);
False: (FValue: TVec1);
end;Part of the implementation looks like this with an example of the ERROR in comments:
{ TVec1Prop }
class operator TVec1Prop.Implicit(const Value: TVec1Prop): TVec1;
begin
Result := Value.Value;
end;
class operator TVec1Prop.Implicit(const Value: TVec1): TVec1Prop;
begin
// ERROR: WriteLn(UIntPtr(Result.FProp)); writes out a random memory
location
// ERROR: Result.FProp should be nil already but it is not
Result.FProp := nil; // ERROR: Code is generated which attempts to call
release on random garbage
Result.FIndex := 0;
Result.FValue := Value;
end;
function TVec1Prop.GetValue: TVec1;
begin
if FProp = nil then
Result := FValue
else
Result := FProp.GetValue(FIndex);
end;
procedure TVec1Prop.SetValue(Value: TVec1);
begin
if FProp = nil then
FValue := Value
else
FProp.SetValue(Value, FIndex);
end;The problem is happening in a lot of places which use my TVec(n)Prop types, resulting in many AV errors, but again only when I am recompiling my demo programs on 32-bit Linux (with the same compiler source). For example I have a list of TVec1Prop, when I clear the list I am getting AV errors due to some items not being finalized correctly.
What should I do?
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