20.5.1 What the Stub Can Do for You
- This routine arranges for
handle_exceptionto run when your program stops. You must call this subroutine explicitly near the beginning of your program.
- This is the central workhorse, but your program never calls it
explicitly—the setup code arranges for
handle_exceptionto run when a trap is triggered.
handle_exceptiontakes control when your program stops during execution (for example, on a breakpoint), and mediates communications with gdb on the host machine. This is where the communications protocol is implemented;
handle_exceptionacts as the gdb representative on the target machine. It begins by sending summary information on the state of your program, then continues to execute, retrieving and transmitting any information gdb needs, until you execute a gdb command that makes your program resume; at that point,
handle_exceptionreturns control to your own code on the target machine.
- Use this auxiliary subroutine to make your program contain a
breakpoint. Depending on the particular situation, this may be the only
way for gdb to get control. For instance, if your target
machine has some sort of interrupt button, you won't need to call this;
pressing the interrupt button transfers control to
handle_exception—in effect, to gdb. On some machines, simply receiving characters on the serial port may also trigger a trap; again, in that situation, you don't need to call
breakpointfrom your own program—simply running target remote from the host gdb session gets control.
breakpointif none of these is true, or if you simply want to make certain your program stops at a predetermined point for the start of your debugging session.