mingw/info/gdb/Stub-Contents.html

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  18 <h4 class="subsection">What the stub can do for you</h4>
  19
  20    <p>The debugging stub for your architecture supplies these three
  21 subroutines:
  22
  23      <dl>
  24 <dt><code>set_debug_traps</code>
  25      <dd>This routine arranges for <code>handle_exception</code> to run when your
  26 program stops.  You must call this subroutine explicitly near the
  27 beginning of your program.
  28
  29      <br><dt><code>handle_exception</code>
  30      <dd>This is the central workhorse, but your program never calls it
  31 explicitly--the setup code arranges for <code>handle_exception</code> to
  32 run when a trap is triggered.
  33
  34      <p><code>handle_exception</code> takes control when your program stops during
  35 execution (for example, on a breakpoint), and mediates communications
  36 with GDB on the host machine.  This is where the communications
  37 protocol is implemented; <code>handle_exception</code> acts as the GDB
  38 representative on the target machine.  It begins by sending summary
  39 information on the state of your program, then continues to execute,
  40 retrieving and transmitting any information GDB needs, until you
  41 execute a GDB command that makes your program resume; at that point,
  42 <code>handle_exception</code> returns control to your own code on the target
  43 machine.
  44
  45      <br><dt><code>breakpoint</code>
  46      <dd>Use this auxiliary subroutine to make your program contain a
  47 breakpoint.  Depending on the particular situation, this may be the only
  48 way for GDB to get control.  For instance, if your target
  49 machine has some sort of interrupt button, you won't need to call this;
  50 pressing the interrupt button transfers control to
  51 <code>handle_exception</code>--in effect, to GDB.  On some machines,
  52 simply receiving characters on the serial port may also trigger a trap;
  53 again, in that situation, you don't need to call <code>breakpoint</code> from
  54 your own program--simply running <code>target remote</code> from the host
  55 GDB session gets control.
  56
  57      <p>Call <code>breakpoint</code> if none of these is true, or if you simply want
  58 to make certain your program stops at a predetermined point for the
  59 start of your debugging session.
  60 </dl>
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