Chain exceptions while unwinding

py/vm.c

@@ -1456,10 +1456,19 @@ unwind_loop:
                 // catch exception and pass to byte code
                 code_state->ip = exc_sp->handler;
                 mp_obj_t *sp = MP_TAGPTR_PTR(exc_sp->val_sp);
+                #if MICROPY_CPYTHON_EXCEPTION_CHAIN
+                mp_obj_t active_exception = get_active_exception(exc_sp, exc_stack);
+                #endif
                 // save this exception in the stack so it can be used in a reraise, if needed
                 exc_sp->prev_exc = nlr.ret_val;
+                mp_obj_t obj = MP_OBJ_FROM_PTR(nlr.ret_val);
+                #if MICROPY_CPYTHON_EXCEPTION_CHAIN
+                if (active_exception != MP_OBJ_NULL) {
+                    mp_store_attr(obj, MP_QSTR___context__, active_exception);
+                }
+                #endif
                 // push exception object so it can be handled by bytecode
-                PUSH(MP_OBJ_FROM_PTR(nlr.ret_val));
+                PUSH(obj);
                 code_state->sp = sp;
 
             #if MICROPY_STACKLESS

tests/basics/exception_chain.py

@@ -5,7 +5,7 @@ except AttributeError:
     raise SystemExit
 
 def print_exc_info(e):
-    print("exception", type(e), repr(e))
+    print("exception", type(e), e.args)
     print("context", type(e.__context__), e.__suppress_context__)
     print("cause", type(e.__cause__))
 
@@ -44,3 +44,11 @@ try:
         raise RuntimeError() from None
 except Exception as e:
     print_exc_info(e)
+
+try:
+    try:
+        raise RuntimeError()
+    except Exception as inner:
+        1/0
+except Exception as e:
+    print_exc_info(e)

tests/circuitpython/traceback_test_chained.py

@@ -53,3 +53,11 @@ try:
         raise RuntimeError() from None
 except Exception as e:
     print_exc_info(e)
+
+try:
+    try:
+        raise RuntimeError()
+    except Exception as inner:
+        1 / 0
+except Exception as e:
+    print_exc_info(e)

tests/circuitpython/traceback_test_chained.py.exp

@@ -41,3 +41,15 @@ Traceback (most recent call last):
 RuntimeError: 
 ------------------------------------------------------------------------
 
+------------------------------------------------------------------------
+Traceback (most recent call last):
+  File "circuitpython/traceback_test_chained.py", line 59, in <module>
+RuntimeError: 
+
+During handling of the above exception, another exception occurred:
+
+Traceback (most recent call last):
+  File "circuitpython/traceback_test_chained.py", line 61, in <module>
+ZeroDivisionError: division by zero
+------------------------------------------------------------------------
+