Wrote down the invariants of some common objects whose structure is
exposed in header files. Fixed a few comments in these headers.
As we might have expected, writing down invariants systematically exposed a
(minor) bug. In this case, function objects have a writeable func_code
attribute, which could be set to code objects with the wrong number of
free variables. Calling the resulting function segfaulted the interpreter.
Added a corresponding test.
diff --git a/Lib/test/test_funcattrs.py b/Lib/test/test_funcattrs.py
index 381412f..1acfeb5 100644
--- a/Lib/test/test_funcattrs.py
+++ b/Lib/test/test_funcattrs.py
@@ -218,11 +218,11 @@
# Test all predefined function attributes systematically
-def cantset(obj, name, value):
+def cantset(obj, name, value, exception=(AttributeError, TypeError)):
verify(hasattr(obj, name)) # Otherwise it's probably a typo
try:
setattr(obj, name, value)
- except (AttributeError, TypeError):
+ except exception:
pass
else:
raise TestFailed, "shouldn't be able to set %s to %r" % (name, value)
@@ -279,11 +279,20 @@
def test_func_code():
+ a = b = 24
def f(): pass
def g(): print 12
+ def f1(): print a
+ def g1(): print b
+ def f2(): print a, b
verify(type(f.func_code) is types.CodeType)
f.func_code = g.func_code
cantset(f, "func_code", None)
+ # can't change the number of free vars
+ cantset(f, "func_code", f1.func_code, exception=ValueError)
+ cantset(f1, "func_code", f.func_code, exception=ValueError)
+ cantset(f1, "func_code", f2.func_code, exception=ValueError)
+ f1.func_code = g1.func_code
def test_func_defaults():
def f(a, b): return (a, b)