From 8047340d7532ec32bc9f2d603bffc0bc9544297f Mon Sep 17 00:00:00 2001
From: Damien George <damien.p.george@gmail.com>
Date: Thu, 24 Dec 2015 12:47:39 +0000
Subject: [PATCH] py: Handle case of return within the finally block of
 try-finally.

Addresses issue #1636.
---
 py/vm.c                             |   8 +++
 tests/basics/try_finally_return2.py | 104 ++++++++++++++++++++++++++++
 2 files changed, 112 insertions(+)
 create mode 100644 tests/basics/try_finally_return2.py

diff --git a/py/vm.c b/py/vm.c
index 8bf59f1e05..8c7c2265e4 100644
--- a/py/vm.c
+++ b/py/vm.c
@@ -1032,6 +1032,14 @@ unwind_jump:;
 
                 ENTRY(MP_BC_RETURN_VALUE):
                     MARK_EXC_IP_SELECTIVE();
+                    // These next 3 lines pop a try-finally exception handler, if one
+                    // is there on the exception stack.  Without this the finally block
+                    // is executed a second time when the return is executed, because
+                    // the try-finally exception handler is still on the stack.
+                    // TODO Possibly find a better way to handle this case.
+                    if (currently_in_except_block) {
+                        POP_EXC_BLOCK();
+                    }
 unwind_return:
                     while (exc_sp >= exc_stack) {
                         if (MP_TAGPTR_TAG1(exc_sp->val_sp)) {
diff --git a/tests/basics/try_finally_return2.py b/tests/basics/try_finally_return2.py
new file mode 100644
index 0000000000..e3ea5f1eb8
--- /dev/null
+++ b/tests/basics/try_finally_return2.py
@@ -0,0 +1,104 @@
+# test 'return' within the finally block
+# it should swallow the exception
+
+# simple case
+def f():
+    try:
+        raise ValueError()
+    finally:
+        print('finally')
+        return 0
+    print('got here')
+print(f())
+
+# nested, return in outer
+def f():
+    try:
+        try:
+            raise ValueError
+        finally:
+            print('finally 1')
+        print('got here')
+    finally:
+        print('finally 2')
+        return 2
+    print('got here')
+print(f())
+
+# nested, return in inner
+def f():
+    try:
+        try:
+            raise ValueError
+        finally:
+            print('finally 1')
+            return 1
+        print('got here')
+    finally:
+        print('finally 2')
+    print('got here')
+print(f())
+
+# nested, return in inner and outer
+def f():
+    try:
+        try:
+            raise ValueError
+        finally:
+            print('finally 1')
+            return 1
+        print('got here')
+    finally:
+        print('finally 2')
+        return 2
+    print('got here')
+print(f())
+
+# nested with reraise
+def f():
+    try:
+        try:
+            raise ValueError
+        except:
+            raise
+        print('got here')
+    finally:
+        print('finally')
+        return 0
+    print('got here')
+print(f())
+
+# triple nesting with reraise
+def f():
+    try:
+        try:
+            try:
+                raise ValueError
+            except:
+                raise
+        except:
+            raise
+    finally:
+        print('finally')
+        return 0
+print(f())
+
+# exception when matching exception
+def f():
+    try:
+        raise ValueError
+    except NonExistingError:
+        pass
+    finally:
+        print('finally')
+        return 0
+print(f())
+
+# raising exception class, not instance
+def f():
+    try:
+        raise ValueError
+    finally:
+        print('finally')
+        return 0
+print(f())