There is a BCON example typo in http://mongoc.org/libmongoc/current/mongoc_collection_find.html under the The "find" command section.
Where the example states:
query = BCON_NEW ("filter", "{", "foo", BCON_INT32 (1), "}", "sort": "{", "bar", BCON_INT32 (-1), "}"); cursor = mongoc_collection_find (collection, MONGOC_QUERY_NONE, 0, 0, 0, query, NULL, NULL);
The semi colon after 'sort' is invalid, it should be a comma.