assignor: fix rd_list destroy callback type mismatch (#5195) (#5278)

* assignor: fix rd_list destroy callback type mismatch (#5195)

Fix the UBSan warning:
  runtime error: call to function rd_kafka_assignor_destroy through pointer
  to incorrect function type 'void (*)(void *)'

by changing rd_kafka_assignor_destroy to take a void * argument, as
expected by rd_list_init() destroy callbacks, and casting internally
to rd_kafka_assignor_t *. Removed explicit cast from rd_list_init argument rd_kafka_assignor_destroy as it is exactly the type as expected by rd_list_init.

* assignor: fix rd_list destroy callback type mismatch (#5195)
Fix the UBSan warning:
runtime error: call to function rd_kafka_assignor_destroy through pointer
to incorrect function type 'void (*)(void *)'
by adding two callback functions which are of required type and which call destroy callbacks internally. rd_list_init uses these new callbacks.
1. rd_kafka_assignor_topic_free(void *ptr) - calls rd_kafka_assignor_topic_destroy after typecasting ptr
2. rd_kafka_assignor_free(void *ptr) - calls rd_kafka_assignor_destroy after typecasting ptr
These new callbacks are used in rd_list_init calls which are of expected types. These wrappers avoid the function type mismatch reported by UBSan while keeping the original destroy helpers typed to their concrete pointer types.

This fixes the UBSan warning about calling the destroy callbacks through pointers with the wrong function type and removes the explicit casts at the rd_list_init() call sites.

Tests:
- UBSan enabled locally to reproduce and verify the issue
- make quick on trivup (./interactive_broker_version.py 3.6.0)

Author: aadish233

src/rdkafka_assignor.c

@@ -240,6 +240,13 @@ static void rd_kafka_assignor_topic_destroy(rd_kafka_assignor_topic_t *at) {
         rd_free(at);
 }
 
+/**
+ * @brief Destroy-variant suitable for rd_list free_cb use.
+ */
+static void rd_kafka_assignor_topic_free(void *ptr) {
+        rd_kafka_assignor_topic_destroy((rd_kafka_assignor_topic_t *)ptr);
+}
+
 int rd_kafka_assignor_topic_cmp(const void *_a, const void *_b) {
         const rd_kafka_assignor_topic_t *a =
             *(const rd_kafka_assignor_topic_t *const *)_a;
@@ -267,7 +274,7 @@ rd_kafka_member_subscriptions_map(rd_kafka_cgrp_t *rkcg,
             rd_kafka_metadata_get_internal(metadata);
 
         rd_list_init(eligible_topics, RD_MIN(metadata->topic_cnt, 10),
-                     (void *)rd_kafka_assignor_topic_destroy);
+                     rd_kafka_assignor_topic_free);
 
         /* For each topic in the cluster, scan through the member list
          * to find matching subscriptions. */
@@ -457,6 +464,13 @@ static void rd_kafka_assignor_destroy(rd_kafka_assignor_t *rkas) {
         rd_free(rkas);
 }
 
+/**
+ * @brief Destroy-variant suitable for rd_list free_cb use.
+ */
+static void rd_kafka_assignor_free(void *ptr) {
+        rd_kafka_assignor_destroy((rd_kafka_assignor_t *)ptr);
+}
+
 
 /**
  * @brief Check that the rebalance protocol of all enabled assignors is
@@ -580,7 +594,7 @@ int rd_kafka_assignors_init(rd_kafka_t *rk, char *errstr, size_t errstr_size) {
         int idx = 0;
 
         rd_list_init(&rk->rk_conf.partition_assignors, 3,
-                     (void *)rd_kafka_assignor_destroy);
+                     rd_kafka_assignor_free);
 
         /* Initialize builtin assignors (ignore errors) */
         rd_kafka_range_assignor_init(rk);