mingw/info/gdb/Breakpoints.html

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  12 Node:<a name="Breakpoints">Breakpoints</a>,
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  17
  18 <h3 class="section">Breakpoints, watchpoints, and catchpoints</h3>
  19
  20    <p>A <dfn>breakpoint</dfn> makes your program stop whenever a certain point in
  21 the program is reached.  For each breakpoint, you can add conditions to
  22 control in finer detail whether your program stops.  You can set
  23 breakpoints with the <code>break</code> command and its variants (see <a href="Set-Breaks.html#Set%20Breaks">Setting breakpoints</a>), to specify the place where your program
  24 should stop by line number, function name or exact address in the
  25 program.
  26
  27    <p>In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
  28 breakpoints in shared libraries before the executable is run.  There is
  29 a minor limitation on HP-UX systems: you must wait until the executable
  30 is run in order to set breakpoints in shared library routines that are
  31 not called directly by the program (for example, routines that are
  32 arguments in a <code>pthread_create</code> call).
  33
  34    <p>A <dfn>watchpoint</dfn> is a special breakpoint that stops your program
  35 when the value of an expression changes.  You must use a different
  36 command to set watchpoints (see <a href="Set-Watchpoints.html#Set%20Watchpoints">Setting watchpoints</a>), but aside from that, you can manage a watchpoint like
  37 any other breakpoint: you enable, disable, and delete both breakpoints
  38 and watchpoints using the same commands.
  39
  40    <p>You can arrange to have values from your program displayed automatically
  41 whenever GDB stops at a breakpoint.  See <a href="Auto-Display.html#Auto%20Display">Automatic display</a>.
  42
  43    <p>A <dfn>catchpoint</dfn> is another special breakpoint that stops your program
  44 when a certain kind of event occurs, such as the throwing of a C<tt>++</tt>
  45 exception or the loading of a library.  As with watchpoints, you use a
  46 different command to set a catchpoint (see <a href="Set-Catchpoints.html#Set%20Catchpoints">Setting catchpoints</a>), but aside from that, you can manage a catchpoint like any
  47 other breakpoint.  (To stop when your program receives a signal, use the
  48 <code>handle</code> command; see <a href="Signals.html#Signals">Signals</a>.)
  49
  50    GDB assigns a number to each breakpoint, watchpoint, or
  51 catchpoint when you create it; these numbers are successive integers
  52 starting with one.  In many of the commands for controlling various
  53 features of breakpoints you use the breakpoint number to say which
  54 breakpoint you want to change.  Each breakpoint may be <dfn>enabled</dfn> or
  55 <dfn>disabled</dfn>; if disabled, it has no effect on your program until you
  56 enable it again.
  57
  58    <p>Some GDB commands accept a range of breakpoints on which to
  59 operate.  A breakpoint range is either a single breakpoint number, like
  60 <code>5</code>, or two such numbers, in increasing order, separated by a
  61 hyphen, like <code>5-7</code>.  When a breakpoint range is given to a command,
  62 all breakpoint in that range are operated on.
  63
  64 <ul class="menu">
  65 <li><a accesskey="1" href="Set-Breaks.html#Set%20Breaks">Set Breaks</a>:                   Setting breakpoints
  66 <li><a accesskey="2" href="Set-Watchpoints.html#Set%20Watchpoints">Set Watchpoints</a>:              Setting watchpoints
  67 <li><a accesskey="3" href="Set-Catchpoints.html#Set%20Catchpoints">Set Catchpoints</a>:              Setting catchpoints
  68 <li><a accesskey="4" href="Delete-Breaks.html#Delete%20Breaks">Delete Breaks</a>:                Deleting breakpoints
  69 <li><a accesskey="5" href="Disabling.html#Disabling">Disabling</a>:                    Disabling breakpoints
  70 <li><a accesskey="6" href="Conditions.html#Conditions">Conditions</a>:                   Break conditions
  71 <li><a accesskey="7" href="Break-Commands.html#Break%20Commands">Break Commands</a>:               Breakpoint command lists
  72 <li><a accesskey="8" href="Breakpoint-Menus.html#Breakpoint%20Menus">Breakpoint Menus</a>:             Breakpoint menus
  73 <li><a accesskey="9" href="Error-in-Breakpoints.html#Error%20in%20Breakpoints">Error in Breakpoints</a>:         ``Cannot insert breakpoints''
  74 </ul>
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