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  1. Thrift
  2. THRIFT-1266

generated C code for iterating over nested maps is wrong




      We are working with Cassandra API in C generated by Thrift and have noticed a bug in the generated code for cassandra_client_send_batch_mutate().

      Full code that Thrift generates for this function is attached, but here is the specification for Cassandra's batch_mutate method:

        Mutate many columns or super columns for many row keys. See also: Mutation.
        mutation_map maps key to column family to a list of Mutation objects to take place at that scope.
      void batch_mutate(1:required map<binary, map<string, list<Mutation>>> mutation_map,
                        2:required ConsistencyLevel consistency_level=ConsistencyLevel.ONE)
           throws (1:InvalidRequestException ire, 2:UnavailableException ue, 3:TimedOutException te),

      If we now look at the generated code, we will notice the following fragment:

      GPtrArray * value;
      g_hash_table_foreach ((GHashTable *)  value, thrift_hash_table_get_keys, &key_list); /* LINE A */

      We can see that in line A it uses the variable "value" as GHashTable, even though the GHashTable "value" was shadowed by GPtrArray "value" a line before.

      Similarly, we can see another fragment below that one, where one instance of variable "value" shadows another instance:

      value = (GPtrArray *) g_hash_table_lookup (((GHashTable *)  value), (gpointer) key); /* LINE B */

      We have worked around the bug in our particular case by renaming one of the "value" variables to "value2" (see "svn di -c 21176 svn://svn.zabbix.com/branches/dev/ZBXNEXT-844/src/libs/zbxcassa/cassandra.c@21176" for a diff), but it would be nice to fix it in Thrift, too.


        1. thrift-1266-c_glib-variable-collision-serializing-nested-maps.patch
          2 kB
          Simon South
        2. batch_mutate.c
          4 kB
          Aleksandrs Saveljevs

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              simonsouth Simon South
              asaveljevs Aleksandrs Saveljevs
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