python: improve convert_tuple_to_char_pointer_array

convert_tuple_to_char_pointer_array now also accepts lists and not only
tuples when converting to a C array. Other fixes:

 - some checking that it's actually a list/tuple before trying to
   convert
 - off-by-a-few-bytes allocation error
   (sizeof(char *)*n+1 vs. sizeof(char *)*(n+1)/calloc(...))

Signed-off-by: Christian Seiler <christian@iwakd.de>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>

src/python-lxc/lxc.c

@@ -34,10 +34,18 @@ typedef struct {
 
 char**
 convert_tuple_to_char_pointer_array(PyObject *argv) {
-    int argc = PyTuple_GET_SIZE(argv);
+    int argc;
     int i, j;
     
-    char **result = (char**) malloc(sizeof(char*)*argc + 1);
+    /* not a list or tuple */
+    if (!PyList_Check(argv) && !PyTuple_Check(argv)) {
+        PyErr_SetString(PyExc_TypeError, "Expected list or tuple.");
+        return NULL;
+    }
+
+    argc = PySequence_Fast_GET_SIZE(argv);
+
+    char **result = (char**) calloc(argc + 1, sizeof(char*));
 
     if (result == NULL) {
         PyErr_SetNone(PyExc_MemoryError);
@@ -45,7 +53,7 @@ convert_tuple_to_char_pointer_array(PyObject *argv) {
     }
 
     for (i = 0; i < argc; i++) {
-        PyObject *pyobj = PyTuple_GET_ITEM(argv, i);
+        PyObject *pyobj = PySequence_Fast_GET_ITEM(argv, i);
         assert(pyobj != NULL);
 
         char *str = NULL;