py: Implement proper re-raising in native codegen's finally handler.

This allows an exception to propagate correctly through a finally
handler.

3 files changed, 14 insertions, 4 deletions

diff --git a/py/emitnative.c b/py/emitnative.c
index 072163618..ad89fb845 100644
--- a/py/emitnative.c
+++ b/py/emitnative.c
@@ -1824,7 +1824,14 @@ STATIC void emit_native_setup_finally(emit_t *emit, mp_uint_t label) {
 }
 
 STATIC void emit_native_end_finally(emit_t *emit) {
-    emit_pre_pop_discard(emit);
+    // logic:
+    //   exc = pop_stack
+    //   if exc == None: pass
+    //   else: raise exc
+    // the check if exc is None is done in the MP_F_NATIVE_RAISE stub
+    vtype_kind_t vtype;
+    emit_pre_pop_reg(emit, &vtype, REG_ARG_1);
+    emit_call(emit, MP_F_NATIVE_RAISE);
     emit_post(emit);
 }
 
diff --git a/py/nativeglue.c b/py/nativeglue.c
index d52eeaeaa..43e7d699f 100644
--- a/py/nativeglue.c
+++ b/py/nativeglue.c
@@ -80,8 +80,11 @@ mp_obj_t mp_native_call_function_n_kw(mp_obj_t fun_in, mp_uint_t n_args_kw, cons
 }
 
 // wrapper that makes raise obj and raises it
-NORETURN void mp_native_raise(mp_obj_t o) {
-    nlr_raise(mp_make_raise_obj(o));
+// END_FINALLY opcode requires that we don't raise if o==None
+void mp_native_raise(mp_obj_t o) {
+    if (o != mp_const_none) {
+        nlr_raise(mp_make_raise_obj(o));
+    }
 }
 
 // these must correspond to the respective enum in runtime0.h
diff --git a/py/runtime.h b/py/runtime.h
index ce87bf07b..1216462b2 100644
--- a/py/runtime.h
+++ b/py/runtime.h
@@ -119,7 +119,7 @@ NORETURN void mp_not_implemented(const char *msg);
 mp_uint_t mp_convert_obj_to_native(mp_obj_t obj, mp_uint_t type);
 mp_obj_t mp_convert_native_to_obj(mp_uint_t val, mp_uint_t type);
 mp_obj_t mp_native_call_function_n_kw(mp_obj_t fun_in, mp_uint_t n_args_kw, const mp_obj_t *args);
-NORETURN void mp_native_raise(mp_obj_t o);
+void mp_native_raise(mp_obj_t o);
 
 extern struct _mp_obj_list_t mp_sys_path_obj;
 extern struct _mp_obj_list_t mp_sys_argv_obj;