Issue #1180193: When importing a module from a .pyc (or .pyo) file with
an existing .py counterpart, override the co_filename attributes of all
code objects if the original filename is obsolete (which can happen if the
file has been renamed, moved, or if it is accessed through different paths).
Patch by Ziga Seilnacht and Jean-Paul Calderone.
diff --git a/Python/import.c b/Python/import.c
index 08024b2..e9ff922 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -909,6 +909,49 @@
 		PySys_WriteStderr("# wrote %s\n", cpathname);
 }
 
+static void
+update_code_filenames(PyCodeObject *co, PyObject *oldname, PyObject *newname)
+{
+	PyObject *constants, *tmp;
+	Py_ssize_t i, n;
+
+	if (!_PyString_Eq(co->co_filename, oldname))
+		return;
+
+	tmp = co->co_filename;
+	co->co_filename = newname;
+	Py_INCREF(co->co_filename);
+	Py_DECREF(tmp);
+
+	constants = co->co_consts;
+	n = PyTuple_GET_SIZE(constants);
+	for (i = 0; i < n; i++) {
+		tmp = PyTuple_GET_ITEM(constants, i);
+		if (PyCode_Check(tmp))
+			update_code_filenames((PyCodeObject *)tmp,
+					      oldname, newname);
+	}
+}
+
+static int
+update_compiled_module(PyCodeObject *co, char *pathname)
+{
+	PyObject *oldname, *newname;
+
+	if (strcmp(PyString_AsString(co->co_filename), pathname) == 0)
+		return 0;
+
+	newname = PyString_FromString(pathname);
+	if (newname == NULL)
+		return -1;
+
+	oldname = co->co_filename;
+	Py_INCREF(oldname);
+	update_code_filenames(co, oldname, newname);
+	Py_DECREF(oldname);
+	Py_DECREF(newname);
+	return 1;
+}
 
 /* Load a source module from a given file and return its module
    object WITH INCREMENTED REFERENCE COUNT.  If there's a matching
@@ -949,6 +992,8 @@
 		fclose(fpc);
 		if (co == NULL)
 			return NULL;
+		if (update_compiled_module(co, pathname) < 0)
+			return NULL;
 		if (Py_VerboseFlag)
 			PySys_WriteStderr("import %s # precompiled from %s\n",
 				name, cpathname);