By: Cary Jensen
Abstract: Tired of always having Delphi integrated debugger load when an exception is raised? It doesn't have to be that way, and this article shows you how in Delphi 7, Delphi 8, and Kylix.
By default, when an exception is encountered by an application that you are
running from the Delphi IDE (integrated development environment), several things
happen. First, your program stops executing. Second, the integrated debugger
loads and details about the exception are displayed in a dialog box.
It takes two or more steps in order to resume your program's
execution. First, you must acknowledge the exception by closing the displayed
dialog box. Next, you must press F9 or click the run button to resume the
execution of your application. Third, you must close the subsequent dialog box
that displays the exception to the end user, which in this case is you. (This
third dialog box is not displayed if the exception was a silent exception or if
the exception was caught and handled in an except block.)
While this behavior is often welcome, there are times when I would prefer
that the integrated debugger did not load. Instead, I would prefer to simply see
the exception as the end user would see it, reducing the number of steps that it
takes to continue testing the application.
For example, imagine that you are testing a database application, and that
you raise an exception from a ClientDataSet's BeforePost method when your code
determines that the record being posted is invalid. While testing the
application, I would prefer to only see the error message describing to the end
user why the record is being rejected without having the integrated debugger
Here is another example. Imagine that you are writing an application using an
Internet Direct (Indy) TIdTCPClient component to retrieve HTML from a Web site
for parsing. With that component, you continue to call Read until it raises an
exception, which signals that the page has finished downloading and the
connection has been closed by the server.
Having the integrated debugger load when this exception occurs is nothing
more than a nuisance. The exception is not really an error. It's really just a signal to your program. And by default, even if you are reading from the
TIdTCPClient within a try-except clause, your application will still stop and
the integrated debugger will load.
There are three ways to prevent the debugger from loading every time an
exception occurs. The first is to disable the debugger altogether. You do this
by unchecking the Integrated debugging check box on the Debugger Options dialog
box in Delphi 7 and Kylix. Display this dialog box, shown in the following
figure, by selecting Tools | Debugger Options.
In Delphi 8, this checkbox is on the Options dialog box when the Debugger
Options node is selected, as shown in the following figure. Display the Options
dialog box by selecting Tools | Options from Delphi 8's main menu.
This approach is overkill, though. Breakpoints do not work when the integrated debugger
is not enabled. Similarly, the various Debugger
windows, such as the Modules, Watches, or the Event Log are inactive when the
Integrated Debugger is disabled. Consequently, I generally do not use this
The second technique is to configure the debugger to ignore exceptions. There are two ways to do this. In Delphi 7 and
Kylix, the easiest is to view the Debugger Options dialog box, select the
Language Exceptions tab, and uncheck the Stop on Delphi Exceptions check box,
shown in the following figure. Now, breakpoints will load the integrated
debugger, but exceptions will not. Furthermore, Debugger windows will continue
to be available.
In Delphi 8, select the Language Exceptions node from the Options dialog box,
as shown in the following figure.
To resume the default behavior, simply check the Stop on Delphi Exceptions
check box once again.
The second way to disable the integrated debugger from loading in response to
an exception is to use breakpoints. I discussed this technique in the article
Non-Breaking Breakpoints in Delphi," which is published here on the
Borland Developer Network. Consequently, I will not repeat that information
again in this article.
The third technique is to tell the integrated debugger to ignore all
exceptions of a particular class or group of classes. This technique also
involves the Language Exceptions tab of the Debugger Options dialog box in
Delphi 7 and Kylix, and the Language Exceptions node from the Options dialog box in Delphi
Here's how you do it. Leave Stop on Delphi Exceptions checked (as well as
Integrated debugging). Click the Add button on the Language Exceptions pane and
add the name of the exception class that you want the integrated debugger to
When an exception is raised, the integrated debugger will check to see if the
raised exception is an instance of one of the classes whose names appear checked
in the Exception Types to Ignore list. If the exception is one of these classes,
or descends from one of these classes, the integrated debugger is not loaded.
If at some later time you do want the integrated debugger to load when a
listed exception is raised, either uncheck the check box next to the exception's
class name in the Exception Types to Ignore list, or select the exception class
name and click the Remove button.
Cary Jensen is President of Jensen Data Systems, Inc., a training
and consulting company that won the 2002 and 2003 Delphi Informant Magazine
Readers Choice Awards for Best Training. He is the author and presenter for
Delphi Developer Days 2004 (www.DelphiDeveloperDays.com) and Advantage Developer Days 2004
information-packed seminars that tour North America and
Cary is also an award-winning, best-selling co-author of nineteen books,
including Advantage Database Server: The Official Guide (2003,
McGraw-Hill/Osborne), Building Kylix Applications (2001, Osborne/McGraw-Hill),
Oracle JDeveloper (1999, Oracle Press), JBuilder Essentials (1998,
Osborne/McGraw-Hill), and Delphi In Depth (1996, Osborne/McGraw-Hill). For information about onsite training and
consulting you can contact Cary at firstname.lastname@example.org, or visit his
Web site at www.JensenDataSystems.com.
) 2004 Cary Jensen, Jensen Data Systems, Inc.
ALL RIGHTS RESERVED. NO PART OF THIS DOCUMENT CAN BE COPIED IN ANY FORM WITHOUT
THE EXPRESS, WRITTEN CONSENT OF THE AUTHOR.
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