BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Deleting COM object          BorlandTalk.com Forum Index -> C++ Builder (ActiveX) View previous topic :: View next topic   Author Message LarryJ Guest Posted: Fri Mar 09, 2007 5:13 pm    Post subject: Deleting COM object Destroying my COM object is causing an exception when I exit my application. When I exit my program I am getting a "Debugger Exception Notification" that stops in the file "system.pas" on, "procedure TObject.Free;" This is line 8314 Below shows how I declare, create and destroy the COM object. I have TC.Unbind(); in the OnClose() event which is where I normally free all resources. . If the COM object is not created, and destroyed then this exception does not occur. When the project settings are no debugger and no CodeGuard this exception appears as a generic access violation message. What am I doing wrong here? // Declare TCOM_cTC2000 TC; // Create HRESULT hr = TC.CreateInstance( CLSID_cTC2000 ); // Destroy if( TC ){ TC.Unbind(); } // Debugger Exception Notification procedure TObject.Free; begin if Self <> nil then Destroy; end; Thanks Larry Johnson. Back to top Remy Lebeau (TeamB) Guest Posted: Fri Mar 09, 2007 11:30 pm    Post subject: Re: Deleting COM object "LarryJ" <LarryJ33 (AT) austin (DOT) rr.com> wrote in message news:45f1412c$1 (AT) newsgroups (DOT) borland.com... Quote: What am I doing wrong here? Nothing at all, so the error has to be something else. What else are you doing with the COM object? Are you using any other interfaces from it? Notification sinks, maybe? Gambit Back to top LarryJ Guest Posted: Sat Mar 10, 2007 9:10 am    Post subject: Re: Deleting COM object When I place a break point in the FormClose() and use F8 to step through the code until the program is closed there is no access violation and no Debugger Exception. If I just close the program the Debugger Exception is given. When I Unbind in FormClose() do I need to pause and wait for the computer to process the Unbind before continuing on with the close process? I have never seen this behavior before but it occurs like this each time. Thanks Larry Johnson. "Remy Lebeau (TeamB)" <no.spam (AT) no (DOT) spam.com> wrote in message news:45f199c0 (AT) newsgroups (DOT) borland.com... > Back to top Remy Lebeau (TeamB) Guest Posted: Sun Mar 11, 2007 12:57 am    Post subject: Re: Deleting COM object "LarryJ" <LarryJ33 (AT) austin (DOT) rr.com> wrote in message news:45f24b16$1 (AT) newsgroups (DOT) borland.com... Quote: When I Unbind in FormClose() do I need to pause and wait for the computer to process the Unbind before continuing on with the close process? No. Quote: I have never seen this behavior before but it occurs like this each time. Then something else is going on. TComInterface is not derived from TObject, so the fact that you are getting an error in TObject suggests that TComInterface is not responsible for the error. The only way it could be is if the TComInterface is a member of your TForm, the offending TObject that is crashing is the TForm object, and the TComInterface's internal memory has been mistakenly overwritten so that its destructor thinks the interface point is still assigned when it really isn't. Gambit Back to top LarryJ Guest Posted: Mon Mar 12, 2007 5:46 pm    Post subject: Re: Deleting COM object Here is the unbelieveable situation! In my FormCloseQuery() I use the Application->MessageBox(...) as seen below. If my app has created the COM object and then runs this Application->MessageBox(...) in FormCloseQuery() when the program moves to cleanup all the memory it will try to run "procedure TObject.Free;" and free a memory location that is invalid. This causes a series of EAccess Violation as the program closes and the Debugger Exception Notification is shown. I found that if I create the COM object and then my app hits ANY Application->MessageBox(...) before closing, when the program closes this same EAccess Violation will occur. So there seems to be a connection between my COM object and Application->MessageBox(...) . I have no idea how to explain this behavior. \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/ int ExitCode=0; msg1 = "Save Charts Before Exit"; ExitCode = Application->MessageBox(msg1.c_str(), "Warning", MB_YESNOCANCEL|MB_ICONWARNING); \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/ HRESULT hr = TC.CreateInstance( CLSID_cTC2000 ); Thanks Larry "Remy Lebeau (TeamB)" <no.spam (AT) no (DOT) spam.com> wrote in message news:45f2ffab$1 (AT) newsgroups (DOT) borland.com... Back to top Remy Lebeau (TeamB) Guest Posted: Mon Mar 12, 2007 10:21 pm    Post subject: Re: Deleting COM object "LarryJ" <LarryJ33 (AT) austin (DOT) rr.com> wrote in message news:45f53d8d$1 (AT) newsgroups (DOT) borland.com... Quote: I found that if I create the COM object and then my app hits ANY Application->MessageBox(...) before closing, when the program closes this same EAccess Violation will occur. So there seems to be a connection between my COM object and Application->MessageBox(...) . I have no idea how to explain this behavior. MessageBox() runs a message queue internally. The only possibility I can think of is if you have a message-based event handler somewhere that is screwing around with memory, such as freeing a pointer somewhere but not NULL'ing it so it tries to be freed a second time later on. It is REALLY hard to diagnose your problem with the very limited code snippets you have shown so far. 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