- for (rem = blob_len(attr), pos = blob_data(attr); \
- rem > 0 && (blob_pad_len(pos) <= rem) && \
- (blob_pad_len(pos) >= sizeof(struct blob_attr)); \
- rem -= blob_pad_len(pos), pos = blob_next(pos))
+ for (rem = attr ? blob_len(attr) : 0, \
+ pos = (struct blob_attr *) (attr ? blob_data(attr) : NULL); \
+ rem > 0 && (blob_pad_len(pos) <= rem) && \
+ (blob_pad_len(pos) >= sizeof(struct blob_attr)); \
+ rem -= blob_pad_len(pos), pos = blob_next(pos))