Error on termination of an application using TRichView

Eugene Kruglov · Post by **Eugene Kruglov** » Tue Oct 09, 2007 9:01 am

Hi, all,

Does anyone know what may happen in application that uses an array of dynamically created/destroyed TRichViewEdits? While a program is running, everything is OK but on termination the following error occurs (the information is derived using JCL Debugger). Also used are TRvaControlPanel, TRichViewActions, TRVPrint.

This error is transient, its conditions are unknown

09.10.2007 14:45:15 Exception EAccessViolation occured at address 00000000
Message: Access violation at address 00000000. Read of address 00000000
Call stack:
[00548247] CRVData.TCustomRVData.Clear (Line 1693, "CRVData.pas")
[0051E415] CRVFData.TCustomRVFormattedData.Clear (Line 774, "CRVFData.pas")

With hope, Eugene

Post by **Sergey Tkachenko** » Tue Oct 09, 2007 12:50 pm

A guess, may be stupid: may you create RichViews dynamically passing some form as an Owner parameter. When this form is freed, it frees all its controls, including these RichViews. When, in some other place, you free all RichViews in your array, and the error occurs.

shmp · Post by **shmp** » Wed Oct 10, 2007 3:31 am

Just a suggestion. When an item (especially a component) has been removed without formatting TRichView, AV usually occurs. On form destroy event, I put rv.clear and rv.format. It did not cause AV anymore.

Hope this may come in handy.

Post by **Sergey Tkachenko** » Wed Oct 10, 2007 7:24 am

When an item (especially a component) has been removed without formatting TRichView, AV usually occurs

It should not happen.

Eugene Kruglov · Post by **Eugene Kruglov** » Wed Oct 10, 2007 10:44 am

shmp wrote:On form destroy event, I put rv.clear and rv.format. It did not cause AV anymore.

I did it, but the error persists... Then I've added the try.. except block in 'CRVData.pas' in place where the error comes from, and all was finished. The benefit from doing this is elimination of annoying OS's window which offers to send to Microsoft a report about an error

But this error however occurs, it is visible in application's log file. What's up, I don't know.

Post by **Sergey Tkachenko** » Wed Oct 10, 2007 11:30 am

Place a breakpoint in TRichView.Destroy. Calculate how many times it is called (may be it is called twice for the same TRichView)

shmp · Post by **shmp** » Thu Oct 11, 2007 2:49 am

My simple guess is that an item (notably a component) has an event created for it. If the item is removed but the event is still triggered, the AV is unavoidable. The clear and format doesn't help anyway. It is only a guess and the problem could be other things.

Post by **Sergey Tkachenko** » Thu Oct 11, 2007 8:21 am

Yes, I agree, it is highly possible that this error occurs because of code in some event. Error occurs when accessing some component on form that is already destroyed.

Eugene Kruglov · Post by **Eugene Kruglov** » Thu Oct 11, 2007 11:32 am

I will try your suggestions, then report... Thank you for attention!