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Access Violation when freeing a child form

Posted on 2002-07-29
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Last Modified: 2010-04-04
I'm writing an MDI app. When the child forms are closed I want them to close rather than be minimised, so I've added

Action := caFree;

to the form's OnClose event. Now whenever the child form is closed I get

Project Calls.exe raised exception class EAccessViolation with message 'Access violation at address 00000000. Read of address 00000000'. Process stopped etc

If I don't add the action := cafree line the form minimises and I don't get an error.

Thanks for your help.
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Question by:riccohb
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15 Comments
 
LVL 27

Expert Comment

by:kretzschmar
ID: 7186042
too rare information,

caFree work normally properly,
there must be some other

maybe a object-reference on the form,
which is lost if you free the form

meikl ;-)
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LVL 12

Expert Comment

by:Lee_Nover
ID: 7186509
yep, most probably reference to some freed pointer (object)
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Expert Comment

by:jsweby
ID: 7186523
Is "Action := caFree" the last line in your FormClose event?

J.
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Author Comment

by:riccohb
ID: 7187384
I've just added a blank form to the project with just Action := caFree in the form's OnClose event and the problem still happened.

jsweby - yes, it is the last line. Usually it's the only line in that procedure.
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Expert Comment

by:jsweby
ID: 7187389
Can you show us how you are creating the form - the whole procedure where you decide you want to show the form.

J.
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Accepted Solution

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swift99 earned 100 total points
ID: 7189063
It sounds like your master form is looking at an object on the form you're freeing.  Or you may have a recursive reference.
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Author Comment

by:riccohb
ID: 7190145
The master form was, as you say, referencing the form immediately after it closed.

I'll also give points to jsweby in a 'points for jsweby' question.

Thanks folks.
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LVL 27

Expert Comment

by:kretzschmar
ID: 7190153
and me?

at least i suggested
>maybe a object-reference on the form,
>which is lost if you free the form
first

meikl ;-)

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LVL 27

Expert Comment

by:kretzschmar
ID: 7190154
maybe i was ignored :-(
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Author Comment

by:riccohb
ID: 7190185
Sorry Kretzschmar. I inadvertently overlooked you. An honest mistake! I've just awarded my last 40 points to jsweby but I'm about to go on an answering spree to earn more points, and when I do I'll ask a 'points for kretzschmar' question.
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Expert Comment

by:kretzschmar
ID: 7193144
well, ok ;-)
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LVL 27

Expert Comment

by:kretzschmar
ID: 7202799
some days ago . . .
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Author Comment

by:riccohb
ID: 7202818
Patience...
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Author Comment

by:riccohb
ID: 7216422
Kretzchmar - I've now posted your 'points for Kretzschmar' question.
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Expert Comment

by:kretzschmar
ID: 7216430
thanks
yippi :-))
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