Merge pull request #390 from pfalcon/reraise-recursive

vm: Save current active exception on opening new try block.

py/bc.h

@@ -9,6 +9,8 @@ typedef struct _mp_exc_stack {
     const byte *handler;
     // bit 0 is saved currently_in_except_block value
     mp_obj_t *val_sp;
+    // Saved exception, valid if currently_in_except_block bit is 1
+    mp_obj_t prev_exc;
     // We might only have 2 interesting cases here: SETUP_EXCEPT & SETUP_FINALLY,
     // consider storing it in bit 1 of val_sp. TODO: SETUP_WITH?
     byte opcode;

py/vm.c

@@ -51,10 +51,12 @@ typedef enum {
     exc_sp->opcode = op; \
     exc_sp->handler = ip + unum; \
     exc_sp->val_sp = MP_TAGPTR_MAKE(sp, currently_in_except_block); \
+    exc_sp->prev_exc = nlr.ret_val; \
     currently_in_except_block = 0; /* in a try block now */
 
 #define POP_EXC_BLOCK() \
     currently_in_except_block = MP_TAGPTR_TAG(exc_sp->val_sp); /* restore previous state */ \
+    if (currently_in_except_block) { nlr.ret_val = exc_sp->prev_exc; } \
     exc_sp--; /* pop back to previous exception handler */
 
 mp_vm_return_kind_t mp_execute_byte_code(const byte *code, const mp_obj_t *args, uint n_args, const mp_obj_t *args2, uint n_args2, mp_obj_t *ret) {

tests/basics/try-reraise2.py

+# Reraise not the latest occured exception
+def f():
+    try:
+        raise ValueError("val", 3)
+    except:
+        try:
+            raise TypeError
+        except:
+            try:
+                try:
+                    raise AttributeError
+                except:
+                    pass
+                raise
+            except TypeError:
+                pass
+        # This should raise original ValueError, not the most recently occurred AttributeError
+        raise
+
+try:
+    f()
+except ValueError as e:
+    print(repr(e))