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| <h3 class="section">5.1 Breakpoints, Watchpoints, and Catchpoints</h3> |
| |
| <p><a name="index-breakpoints-199"></a>A <dfn>breakpoint</dfn> makes your program stop whenever a certain point in |
| the program is reached. For each breakpoint, you can add conditions to |
| control in finer detail whether your program stops. You can set |
| breakpoints with the <code>break</code> command and its variants (see <a href="Set-Breaks.html#Set-Breaks">Setting Breakpoints</a>), to specify the place where your program |
| should stop by line number, function name or exact address in the |
| program. |
| |
| <p>On some systems, you can set breakpoints in shared libraries before |
| the executable is run. There is a minor limitation on HP-UX systems: |
| you must wait until the executable is run in order to set breakpoints |
| in shared library routines that are not called directly by the program |
| (for example, routines that are arguments in a <code>pthread_create</code> |
| call). |
| |
| <p><a name="index-watchpoints-200"></a><a name="index-data-breakpoints-201"></a><a name="index-memory-tracing-202"></a><a name="index-breakpoint-on-memory-address-203"></a><a name="index-breakpoint-on-variable-modification-204"></a>A <dfn>watchpoint</dfn> is a special breakpoint that stops your program |
| when the value of an expression changes. The expression may be a value |
| of a variable, or it could involve values of one or more variables |
| combined by operators, such as ‘<samp><span class="samp">a + b</span></samp>’. This is sometimes called |
| <dfn>data breakpoints</dfn>. You must use a different command to set |
| watchpoints (see <a href="Set-Watchpoints.html#Set-Watchpoints">Setting Watchpoints</a>), but aside |
| from that, you can manage a watchpoint like any other breakpoint: you |
| enable, disable, and delete both breakpoints and watchpoints using the |
| same commands. |
| |
| <p>You can arrange to have values from your program displayed automatically |
| whenever <span class="sc">gdb</span> stops at a breakpoint. See <a href="Auto-Display.html#Auto-Display">Automatic Display</a>. |
| |
| <p><a name="index-catchpoints-205"></a><a name="index-breakpoint-on-events-206"></a>A <dfn>catchpoint</dfn> is another special breakpoint that stops your program |
| when a certain kind of event occurs, such as the throwing of a C<tt>++</tt> |
| exception or the loading of a library. As with watchpoints, you use a |
| different command to set a catchpoint (see <a href="Set-Catchpoints.html#Set-Catchpoints">Setting Catchpoints</a>), but aside from that, you can manage a catchpoint like any |
| other breakpoint. (To stop when your program receives a signal, use the |
| <code>handle</code> command; see <a href="Signals.html#Signals">Signals</a>.) |
| |
| <p><a name="index-breakpoint-numbers-207"></a><a name="index-numbers-for-breakpoints-208"></a><span class="sc">gdb</span> assigns a number to each breakpoint, watchpoint, or |
| catchpoint when you create it; these numbers are successive integers |
| starting with one. In many of the commands for controlling various |
| features of breakpoints you use the breakpoint number to say which |
| breakpoint you want to change. Each breakpoint may be <dfn>enabled</dfn> or |
| <dfn>disabled</dfn>; if disabled, it has no effect on your program until you |
| enable it again. |
| |
| <p><a name="index-breakpoint-ranges-209"></a><a name="index-ranges-of-breakpoints-210"></a>Some <span class="sc">gdb</span> commands accept a range of breakpoints on which to |
| operate. A breakpoint range is either a single breakpoint number, like |
| ‘<samp><span class="samp">5</span></samp>’, or two such numbers, in increasing order, separated by a |
| hyphen, like ‘<samp><span class="samp">5-7</span></samp>’. When a breakpoint range is given to a command, |
| all breakpoints in that range are operated on. |
| |
| <ul class="menu"> |
| <li><a accesskey="1" href="Set-Breaks.html#Set-Breaks">Set Breaks</a>: Setting breakpoints |
| <li><a accesskey="2" href="Set-Watchpoints.html#Set-Watchpoints">Set Watchpoints</a>: Setting watchpoints |
| <li><a accesskey="3" href="Set-Catchpoints.html#Set-Catchpoints">Set Catchpoints</a>: Setting catchpoints |
| <li><a accesskey="4" href="Delete-Breaks.html#Delete-Breaks">Delete Breaks</a>: Deleting breakpoints |
| <li><a accesskey="5" href="Disabling.html#Disabling">Disabling</a>: Disabling breakpoints |
| <li><a accesskey="6" href="Conditions.html#Conditions">Conditions</a>: Break conditions |
| <li><a accesskey="7" href="Break-Commands.html#Break-Commands">Break Commands</a>: Breakpoint command lists |
| <li><a accesskey="8" href="Save-Breakpoints.html#Save-Breakpoints">Save Breakpoints</a>: How to save breakpoints in a file |
| <li><a accesskey="9" href="Error-in-Breakpoints.html#Error-in-Breakpoints">Error in Breakpoints</a>: ``Cannot insert breakpoints'' |
| <li><a href="Breakpoint_002drelated-Warnings.html#Breakpoint_002drelated-Warnings">Breakpoint-related Warnings</a>: ``Breakpoint address adjusted...'' |
| </ul> |
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