Add code in VM to handle nested exceptions correctly.
diff --git a/py/vm.c b/py/vm.c
index b10d641..0a7c2fb 100644
--- a/py/vm.c
+++ b/py/vm.c
@@ -61,8 +61,8 @@
mp_obj_t fast0 = fastn[0], fast1 = fastn[1], fast2 = fastn[2];
nlr_buf_t nlr;
- // on the exception stack we store (ip, sp) for each block
- machine_uint_t exc_stack[8];
+ volatile machine_uint_t currently_in_except_block = 0; // 0 or 1, to detect nested exceptions
+ machine_uint_t exc_stack[8]; // on the exception stack we store (ip, sp | X) for each block, X = previous value of currently_in_except_block
machine_uint_t *volatile exc_sp = &exc_stack[-1]; // stack grows up, exc_sp points to top of stack
// outer exception handling loop
@@ -275,7 +275,8 @@
case MP_BC_SETUP_EXCEPT:
DECODE_ULABEL; // except labels are always forward
*++exc_sp = (machine_uint_t)ip + unum;
- *++exc_sp = (machine_uint_t)sp;
+ *++exc_sp = (((machine_uint_t)sp) | currently_in_except_block);
+ currently_in_except_block = 0; // in a try block now
break;
case MP_BC_END_FINALLY:
@@ -313,7 +314,8 @@
assert(exc_sp >= &exc_stack[0]);
//sp = (mp_obj_t*)(*exc_sp--);
//exc_sp--; // discard ip
- exc_sp -= 2;
+ currently_in_except_block = (exc_sp[0] & 1); // restore previous state
+ exc_sp -= 2; // pop back to previous exception handler
//sp += 3; // pop 3 exception values
break;
@@ -466,16 +468,33 @@
} else {
// exception occurred
+ while (currently_in_except_block) {
+ // nested exception
+
+ assert(exc_sp >= &exc_stack[0]);
+
+ // TODO make a proper message for nested exception
+ // at the moment we are just raising the very last exception (the one that caused the nested exception)
+
+ // move up to previous exception handler
+ currently_in_except_block = (exc_sp[0] & 1); // restore previous state
+ exc_sp -= 2; // pop back to previous exception handler
+ }
+
if (exc_sp >= &exc_stack[0]) {
+ // set flag to indicate that we are now handling an exception
+ currently_in_except_block = 1;
+
// catch exception and pass to byte code
- sp = (mp_obj_t*)(exc_sp[0]);
+ sp = (mp_obj_t*)(exc_sp[0] & (~((machine_uint_t)1)));
ip = (const byte*)(exc_sp[-1]);
// push(traceback, exc-val, exc-type)
PUSH(mp_const_none);
PUSH(nlr.ret_val);
PUSH(mp_const_none);
+
} else {
- // re-raise exception
+ // re-raise exception to higher level
// TODO what to do if this is a generator??
nlr_jump(nlr.ret_val);
}