py: Add MICROPY_VM_HOOK_EXC for exception-to-bytecode handoff.

New VM hook that fires when an unhandled exception is passed to byte
code for handling by a try/except block. Unlike MICROPY_NLR_RAISE_HOOK
which fires on every nlr_raise (including internal StopIteration, import
probes, etc.), this hook only fires when an exception actually reaches
a Python exception handler.

Signed-off-by: iabdalkader <[email protected]>

Author: iabdalkader

py/mpconfig.h

@@ -737,6 +737,11 @@ typedef uint64_t mp_uint_t;
 #define MICROPY_VM_HOOK_RETURN
 #endif
 
+// Hook for the VM when an unhandled exception is passed to byte code
+#ifndef MICROPY_VM_HOOK_EXC
+#define MICROPY_VM_HOOK_EXC
+#endif
+
 // Hook for mp_sched_schedule when a function gets scheduled on sched_queue
 // (this macro executes within an atomic section)
 #ifndef MICROPY_SCHED_HOOK_SCHEDULED

py/vm.c

@@ -1476,6 +1476,7 @@ unwind_jump:;
 
             if (exc_sp >= exc_stack) {
                 // catch exception and pass to byte code
+                MICROPY_VM_HOOK_EXC
                 code_state->ip = exc_sp->handler;
                 mp_obj_t *sp = MP_TAGPTR_PTR(exc_sp->val_sp);
                 // save this exception in the stack so it can be used in a reraise, if needed