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Using the Debugger
Conditional Breakpoints
NOTE
NOTE
In the case of a conditional breakpoint, program execution is paused only when predefined
conditions are met. To create a conditional breakpoint, first set the breakpoint in the Code
Editor. Then choose View | Breakpoints from the main menu to display the Breakpoint list
dialog box. Right-click on the breakpoint for which you want to set conditions and choose
Properties from the speed menu. When the Edit breakpoint dialog box is displayed, set the
conditions for the breakpoint.
Conditional breakpoints come in two flavors. The first type is a conditional expression
breakpoint. Enter the conditional expression in the Condition field of the Edit breakpoint
dialog box (refer to Figure 11.3). When the program runs, the conditional expression is
evaluated each time the breakpoint is encountered. When the conditional expression
evaluates to true, program execution is halted. If the condition does not evaluate to true, the
breakpoint is ignored. For example, look back at the last breakpoint in the Breakpoint list
window shown in Figure 11.2. This breakpoint has a conditional expression of x > 10. If at
some point in the execution of the program x is greater than 10, the program will stop at the
breakpoint. If x is never greater than 10, program execution will not stop at the breakpoint.
The other type of conditional breakpoint is the pass count breakpoint. With a pass count
breakpoint, program execution is paused only after the breakpoint is encountered the
specified number of times. To specify a pass count breakpoint, edit the breakpoint and specify
a value for the Pass count field in the Edit breakpoint dialog box. Figure 11.2 shows a
breakpoint that has the pass count set to 3. Program execution will stop at this breakpoint
the third time the breakpoint is encountered.
The pass count is 1 based and not 0 based. As indicated in the previous
example, a pass count of 3 means that the breakpoint will be valid the
third time the breakpoint is encountered by the program.
Use pass count breakpoints when you need your program to execute through a breakpoint
a certain number of times before you break to inspect variables, step through code, or
something similar.
Conditional breakpoints will slow down the normal execution of the
program because the conditions need to be evaluated each time a
conditional breakpoint is encountered. If your program is acting sluggish
during debugging, check your breakpoints in the breakpoint list and see
whether you have conditional breakpoints that you have forgotten about.
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