mingw/info/gdb/Jumping.html

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  19 <h3 class="section">Continuing at a different address</h3>
  20
  21    <p>Ordinarily, when you continue your program, you do so at the place where
  22 it stopped, with the <code>continue</code> command.  You can instead continue at
  23 an address of your own choosing, with the following commands:
  24
  25      <dl>
  26 <dt><code>jump </code><var>linespec</var><code></code>
  27      <dd>Resume execution at line <var>linespec</var>.  Execution stops again
  28 immediately if there is a breakpoint there.  See <a href="List.html#List">Printing source lines</a>, for a description of the different forms of
  29 <var>linespec</var>.  It is common practice to use the <code>tbreak</code> command
  30 in conjunction with <code>jump</code>.  See <a href="Set-Breaks.html#Set%20Breaks">Setting breakpoints</a>.
  31
  32      <p>The <code>jump</code> command does not change the current stack frame, or
  33 the stack pointer, or the contents of any memory location or any
  34 register other than the program counter.  If line <var>linespec</var> is in
  35 a different function from the one currently executing, the results may
  36 be bizarre if the two functions expect different patterns of arguments or
  37 of local variables.  For this reason, the <code>jump</code> command requests
  38 confirmation if the specified line is not in the function currently
  39 executing.  However, even bizarre results are predictable if you are
  40 well acquainted with the machine-language code of your program.
  41
  42      <br><dt><code>jump *</code><var>address</var><code></code>
  43      <dd>Resume execution at the instruction at address <var>address</var>.
  44 </dl>
  45
  46    <p>On many systems, you can get much the same effect as the <code>jump</code>
  47 command by storing a new value into the register <code>$pc</code>.  The
  48 difference is that this does not start your program running; it only
  49 changes the address of where it <em>will</em> run when you continue.  For
  50 example,
  51
  52 <pre class="example">     set $pc = 0x485
  53      </pre>
  54
  55 <p>makes the next <code>continue</code> command or stepping command execute at
  56 address <code>0x485</code>, rather than at the address where your program stopped.
  57 See <a href="Continuing-and-Stepping.html#Continuing%20and%20Stepping">Continuing and stepping</a>.
  58
  59    <p>The most common occasion to use the <code>jump</code> command is to back
  60 up--perhaps with more breakpoints set--over a portion of a program
  61 that has already executed, in order to examine its execution in more
  62 detail.
  63
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