MDEV-20778 UBSAN: call to function free_rpl_filter() through pointer to incorrect function type

Proper C-style type erasure is done via void*, not via char* or something else.

free_key_cache()
free_rpl_filter(): types were fixed to avoid function pointer type cast which
is still undefined behavior.

Note, that casting from void* to any other pointer type is safe and correct.

sql/keycaches.cc

@@ -84,7 +84,7 @@ bool NAMED_ILIST::delete_element(const char *name, uint length, void (*free_elem
   DBUG_RETURN(1);
 }
 
-void NAMED_ILIST::delete_elements(void (*free_element)(const char *name, uchar*))
+void NAMED_ILIST::delete_elements(void (*free_element)(const char *name, void*))
 {
   NAMED_ILINK *element;
   DBUG_ENTER("NAMED_ILIST::delete_elements");
@@ -156,9 +156,9 @@ KEY_CACHE *get_or_create_key_cache(const char *name, uint length)
 }
 
 
-void free_key_cache(const char *name, KEY_CACHE *key_cache)
+void free_key_cache(const char *name, void *key_cache)
 {
-  end_key_cache(key_cache, 1);		// Can never fail
+  end_key_cache(static_cast<KEY_CACHE *>(key_cache), 1); // Can never fail
   my_free(key_cache);
 }
 
@@ -220,13 +220,12 @@ Rpl_filter *get_or_create_rpl_filter(const char *name, uint length)
   return filter;
 }
 
-void free_rpl_filter(const char *name, Rpl_filter *filter)
+void free_rpl_filter(const char *name, void *filter)
 {
-  delete filter;
-  filter= 0;
+  delete static_cast<Rpl_filter*>(filter);
 }
 
 void free_all_rpl_filters()
 {
-  rpl_filters.delete_elements((void (*)(const char*, uchar*)) free_rpl_filter);
+  rpl_filters.delete_elements(free_rpl_filter);
 }

sql/keycaches.h

@@ -30,7 +30,7 @@ class NAMED_ILINK;
 class NAMED_ILIST: public I_List<NAMED_ILINK>
 {
   public:
-  void delete_elements(void (*free_element)(const char*, uchar*));
+  void delete_elements(void (*free_element)(const char*, void*));
   bool delete_element(const char *name, uint length, void (*free_element)(const char*, uchar*));
 };
 
@@ -42,7 +42,7 @@ extern NAMED_ILIST key_caches;
 KEY_CACHE *create_key_cache(const char *name, uint length);
 KEY_CACHE *get_key_cache(const LEX_STRING *cache_name);
 KEY_CACHE *get_or_create_key_cache(const char *name, uint length);
-void free_key_cache(const char *name, KEY_CACHE *key_cache);
+void free_key_cache(const char *name, void *key_cache);
 bool process_key_caches(process_key_cache_t func, void *param);
 
 /* For Rpl_filter */
@@ -52,7 +52,6 @@ extern NAMED_ILIST rpl_filters;
 Rpl_filter *create_rpl_filter(const char *name, uint length);
 Rpl_filter *get_rpl_filter(LEX_STRING *filter_name);
 Rpl_filter *get_or_create_rpl_filter(const char *name, uint length);
-void free_rpl_filter(const char *name, Rpl_filter *filter);
 void free_all_rpl_filters(void);
 
 #endif /* KEYCACHES_INCLUDED */

sql/mysqld.cc

@@ -2232,7 +2232,7 @@ void clean_up(bool print_message)
   tdc_deinit();
   mdl_destroy();
   dflt_key_cache= 0;
-  key_caches.delete_elements((void (*)(const char*, uchar*)) free_key_cache);
+  key_caches.delete_elements(free_key_cache);
   wt_end();
   multi_keycache_free();
   sp_cache_end();