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<title>KDbg - User's Manual - Breakpoint list</title>
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<p><a href="index.html">Contents</a></p>
<h1>
The Breakpoint List</h1>
<p>The breakpoint list displays all breakpoints and watchpoints that are set
and allows you to manipulate them. It can be displayed using <i>View|Breakpoints</i>.</p>
<h2>
The list of breakpoints</h2>
<p>For each breakpoint the following is shown:</p>
<ul>
<li>
the breakpoint location,</li>
<li>
the hit count,</li>
<li>
the ignore count if set,</li>
<li>
the condition if set.</li>
</ul>
<p>The icon in front of the entry indicates whether the breakpoint is enabled
(a red dot) or disabled (a bright red dot), whether the breakpoint is temporary
(a tiny clock is overlaid), whether the breakpoint is conditional (a
tiny question mark is overlaid), or whether the breakpoint is <em>orphaned</em>
(a 'x' is overlaid).</p>
<p>Watchpoints are indicated by an eye glas icon in front of the line.</p>
<h2>
<A name="orphanedbp"></A>Orphaned breakpoints</h2>
<p><em>Orphaned breakpoints</em> are breakpoints that gdb cannot implant
immediately. Orphaned breakpoints occur if you try to set a breakpoint in a file
that is not part of the executable. In particular, this is the case if the file
belongs to a shared library or dynamically loaded module: When the executable
is loaded, gdb does not yet know about dynamic modules and, hence, cannot set
breakpoints there. However, KDbg does not forget about requests to set
breakpoints in dynamic modules: It tries to set orphaned breakpoints each time
that the program stops. When the breakpoint can be set successfully, it turns
into a normal breakpoint.</p>
<p>But there is an important consequence: Orphaned breakpoints are not effective,
and the program will <em>not</em> stop there. The remedy is to set a breakpoint
in the executable at the earliest possible point after which it is known that
the dynamic module is loaded. For shared libraries this is usually in <tt>main()</tt>
and for dynamically loaded modules it is after the call to <tt>dlopen()</tt>
(or equivalent). When the program stops at this breakpoint the orphaned
breakpoints from the dynamic module are set and become effective.</p>
<h2>
Manipulating breakpoints</h2>
<p><a name="StopProg"></a>It is important to note that breakpoints and watchpoints
cannot be manipulated while the program is running. If the program has
already been started, it must stop first - either by hitting a breakpoint
that is already set or forcefully by choosing <i>Execution|Break</i>. Note
that this will not terminate the program, it just interrupts it. You can
now manipulate the breakpoints; then choose <i>Execution|Continue</i> to
let the program continue.</p>
<p>To set a breakpoint on a specific source line, it is easiest to do this
in the source code window. If you don't know the exact file and line number
of a function, you can set the breakpoint by typing the function name in
the edit box above the list and click <i>Add Breakpoint</i>.</p>
<p>You can disable and enable breakpoints by selecting them in the list
and clicking <i>Disable</i> or <i>Enable</i>. Or you simply click on the
breakpoint in the list using the middle mouse button - just like you enable
and disable breakpoints in the source window.</p>
<p>You can set a condition on a breakpoint (so that the program is only
stopped if the condition is true) or set an ignore count (so that the program
is not stopped the next n times that the breakpoint is hit). To do that,
press the <i>Conditional</i> button and enter the condition and/or ignore
count.</p>
<h2>
Manipulating watchpoints</h2>
<p>Watchpoints are a like breakpoints, except that they interrupt the program
when the value of a memory location changes. As with breakpoints, watchpoints
cannot be manipulated while the program is running. See <a href="#StopProg">above</a>
for more information.</p>
<p>To set a watchpoint, type an expression in the edit box above the list,
then click <i>Add Watchpoint</i>. The program will stop when the value
of the expression changes. Note that watchpoints that involve local variables
can only be set when the program is stopped in a breakpoint (or has been
interrupted by <i>Execution|Break</i>).</p>
<p>To remove the watchpoint, select it from the list and click <i>Remove</i>.
If the expression involves a local variable, the watchpoint will be removed
automatically when the program leaves the current frame.</p>
<p>You can set a condition and an ignore count on the watchpoint just like
on breakpoints by selecting it and clicking <i>Conditional</i>.</p>
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