Access violation when closing Preview Form

rbuser

My specific application is much to complicated to give a good example. When
a preview of a report is closed, I get an access violation. This does not
happen every time, but it seems to vary between different computers that I
run the report on. I am currently using Delphi 5.0 (Build 2195 Service Pack
1), with Report Builder 6.03 standard edition.
If I run the following code on a test project, to rapidly create, print and
destroy reports, I also get an access violation.
This problem started since I started to use V6.03 instead of V5.xxx, because
5.xxx seemed to have a problem with "ShiftRelativeTo" properties when sub
reports with multiple columns were used.

Did anybody else experience any similar problems?

Regards
Ludek


unit Unit1;

interface

uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls;

type
TForm1 = class(TForm)
Button1: TButton;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.DFM}

uses
ppReport;

procedure TForm1.Button1Click(Sender: TObject);
var rpt: TppReport;
i: integer;
begin
for i := 1 to 100000 do
begin
rpt := TppReport.Create(self);
try
rpt.ModalPreview := False;
rpt.Print;
finally
FreeAndNil(rpt);
end;
end;
end;

end.

nicocizik

Hello,

In my testing with your code with Delphi 5 and ReportBuilder 7.03, I was not
able to recreate an AV. This could have been an issue that has been fixed
for the latest release. Please try downloading a trial copy of
ReportBuilder 7.03 and testing with that.

--

rbuser

Well, I found that:

TppCustomReport.Notify was under certain conditions called AFTER the
destructor TppCustomReport.Destroy, leaving FTemplate with the pointer to
the destroyed FTemplate. The reference to FTemplate in
TppCustomReport.Notify then cause access violations.

So I "Modified" rbRCL55.dpk = > rbRCL55.bpl unit ppClass.Pas to get rid of
access violation when closing report preview
By setting FTemplate = nil just after it is freed, and checking for
FTemplate = nil before accessing FTemplate as an object in
TppCustomReport.Notify, the problem seemed to be resolved for the cases
where I could duplicate it.
TppCustomReport = class(TppProducer)
private
......
FTemplate: TppReportTemplate;
....
1. destructor TppCustomReport.Destroy;
begin
.........
.........
{free TPersistent objects}
FTemplate.Free;
{ LDK!!! } FTemplate := nil; // I added this line ...
.........
end;
.............
2. { TppCustomReport.Notify }
procedure TppCustomReport.Notify(aCommunicator: TppCommunicator; aOperation:
TppOperationType);
begin
inherited Notify(aCommunicator, aOperation);
......
else
if assigned(FTemplate) and { LDK !!!! } // I added this line too..
(FTemplate.DatabaseSettings.DataPipeline = aCommunicator) then
FTemplate.DatabaseSettings.DataPipeline := nil;

end; {procedure, Notify}