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Fix core dump in example from Samuele Pedroni: 

from __future__ import nested_scopes
x=7
def f():
    x=1
    def g():
        global x
        def i():
            def h():
                return x
            return h()
        return i()
    return g()

print f()
print x

This kind of code didn't work correctly because x was treated as free
in i, leading to an attempt to load x in g to make a closure for i.

Solution is to make global decl apply to nested scopes unless their is
an assignment.  Thus, x in h is global.
This commit is contained in:
Jeremy Hylton 2001-03-01 06:09:34 +00:00
parent a52e8fe49a
commit 7889107be7
1 changed files with 31 additions and 15 deletions
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46
Python/compile.c
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@ -179,6 +179,8 @@ code_hash(PyCodeObject *co)
return h;
}
/* XXX code objects need to participate in GC? */
PyTypeObject PyCode_Type = {
PyObject_HEAD_INIT(&PyType_Type)
0,
@ -2132,8 +2134,13 @@ com_make_closure(struct compiling *c, PyCodeObject *co)
else /* (reftype == FREE) */
arg = com_lookup_arg(c->c_freevars, name);
if (arg == -1) {
fprintf(stderr, "lookup %s in %s %d %d\n",
PyObject_REPR(name), c->c_name, reftype, arg);
fprintf(stderr, "lookup %s in %s %d %d\n"
"freevars of %s: %s\n",
PyObject_REPR(name),
c->c_name,
reftype, arg,
PyString_AS_STRING(co->co_name),
PyObject_REPR(co->co_freevars));
Py_FatalError("com_make_closure()");
}
com_addoparg(c, LOAD_CLOSURE, arg);
@ -4424,8 +4431,8 @@ symtable_update_free_vars(struct symtable *st)
child = (PySymtableEntryObject *)
PyList_GET_ITEM(ste->ste_children, i);
while (PyDict_Next(child->ste_symbols, &pos, &name, &o)) {
int v = PyInt_AS_LONG(o);
if (!(is_free(v)))
int flags = PyInt_AS_LONG(o);
if (!(is_free(flags)))
continue; /* avoids indentation */
if (list == NULL) {
list = PyList_New(0);
@ -4438,18 +4445,24 @@ symtable_update_free_vars(struct symtable *st)
return -1;
}
}
/*
if (st->st_nested_scopes == 0
&& list && PyList_GET_SIZE(list) > 0) {
fprintf(stderr, "function %s has children with "
"the following free vars:\n%s\n",
PyString_AS_STRING(ste->ste_name),
PyObject_REPR(list));
continue;
}
*/
for (j = 0; list && j < PyList_GET_SIZE(list); j++) {
PyObject *v;
name = PyList_GET_ITEM(list, j);
v = PyDict_GetItem(ste->ste_symbols, name);
/* If a name N is declared global in scope A and
referenced in scope B contained (perhaps
indirectly) in A and there are no scopes
with bindings for N between B and A, then N
is global in B.
*/
if (v) {
int flags = PyInt_AS_LONG(v);
if (flags & DEF_GLOBAL) {
symtable_undo_free(st, child->ste_id,
name);
continue;
}
}
if (ste->ste_nested) {
if (symtable_add_def_o(st, ste->ste_symbols,
name, def) < 0) {
@ -4481,13 +4494,14 @@ symtable_check_global(struct symtable *st, PyObject *child, PyObject *name)
PyObject *o;
int v;
PySymtableEntryObject *ste = st->st_cur;
if (ste->ste_type == TYPE_CLASS)
return symtable_undo_free(st, child, name);
o = PyDict_GetItem(ste->ste_symbols, name);
if (o == NULL)
return symtable_undo_free(st, child, name);
v = PyInt_AS_LONG(o);
if (is_free(v) || (v & DEF_GLOBAL))
return symtable_undo_free(st, child, name);
else
@ -4506,6 +4520,7 @@ symtable_undo_free(struct symtable *st, PyObject *id,
ste = (PySymtableEntryObject *)PyDict_GetItem(st->st_symbols, id);
if (ste == NULL)
return -1;
info = PyDict_GetItem(ste->ste_symbols, name);
if (info == NULL)
return 0;
@ -4938,6 +4953,7 @@ symtable_global(struct symtable *st, node *n)
int i;
if (st->st_nscopes == 1) {
/* XXX must check that we are compiling file_input */
if (symtable_warn(st,
"global statement has no meaning at module level") < 0)
return;