Hardware breakpoint support is also for execution and, oddly, the x86 IO port space reachable by the "in" and "out" instructions. Using an int3 has some proble

Hardware breakpoint support is also for execution and, oddly, the x86 IO port space reachable by the "in" and "out" instructions. Using an int3 has some problems. It can be seen by the code, which may change behavior. For example, a self-checksum would fail. The int3 will affect all threads, while the hardware breakpoint can be made to affect just one thread.