#4617: Previously it was illegal to delete a name from the local
namespace if it occurs as a free variable in a nested block. This limitation
of the compiler has been lifted, and a new opcode introduced (DELETE_DEREF).
This sample was valid in 2.6, but fails to compile in 3.x without this change::
>>> def f():
... def print_error():
... print(e)
... try:
... something
... except Exception as e:
... print_error()
... # implicit "del e" here
This sample has always been invalid in Python, and now works::
>>> def outer(x):
... def inner():
... return x
... inner()
... del x
There is no need to bump the PYC magic number: the new opcode is used
for code that did not compile before.
diff --git a/Python/compile.c b/Python/compile.c
index 6963a15..5341e6b 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -857,6 +857,8 @@
return 1;
case STORE_DEREF:
return -1;
+ case DELETE_DEREF:
+ return 0;
default:
fprintf(stderr, "opcode = %d\n", opcode);
Py_FatalError("opcode_stack_effect()");
@@ -2506,13 +2508,7 @@
case AugLoad:
case AugStore:
break;
- case Del:
- PyErr_Format(PyExc_SyntaxError,
- "can not delete variable '%S' referenced "
- "in nested scope",
- name);
- Py_DECREF(mangled);
- return 0;
+ case Del: op = DELETE_DEREF; break;
case Param:
default:
PyErr_SetString(PyExc_SystemError,