MDEV-34237: On Startup: UBSAN: runtime error: call to function...

MDEV-34237: On Startup: UBSAN: runtime error: call to function MDL_lock::lf_hash_initializer lf_hash_insert through pointer to incorrect function type 'void (*)(st_lf_hash *, void *, const void *)'

A few different incorrect function type UBSAN issues have been
grouped into this patch.

The only real potentially undefined behavior is an error about
show_func_mutex_instances_lost, which when invoked in
sql_show.cc::show_status_array(), puts 5 arguments onto the stack;
however, the implementing function only actually has 3 parameters (so
only 3 would be popped). This was fixed by adding in the remaining
parameters to satisfy the type mysql_show_var_func.

The rest of the findings are pointer type mismatches that wouldn't
lead to actual undefined behavior. The lf_hash_initializer function
type definition is

typedef void (*lf_hash_initializer)(LF_HASH *hash, void *dst, const void *src);

but the MDL_lock and table cache's implementations of this function
do not have that signature. The MDL_lock has specific MDL object
parameters:

static void lf_hash_initializer(LF_HASH *hash __attribute__((unused)),
                                MDL_lock *lock, MDL_key *key_arg)

and the table cache has specific TDC parameters:

static void tdc_hash_initializer(LF_HASH *,
                                 TDC_element *element, LEX_STRING *key)

leading to UBSAN runtime errors when invoking these functions.

This patch fixes these type mis-matches by changing the
implementing functions to use void * and const void * for their
respective parameters, and later casting them to their expected
type in the function body.

Note too the functions tdc_hash_key and tc_purge_callback had
a similar problem to tdc_hash_initializer and was fixed
similarly.

Reviewed By:
============
Sergei Golubchik <serg@mariadb.com>

sql/mdl.cc

@@ -673,8 +673,10 @@ class MDL_lock
   { ((MDL_lock*)(arg + LF_HASH_OVERHEAD))->~MDL_lock(); }
 
   static void lf_hash_initializer(LF_HASH *hash __attribute__((unused)),
-                                  MDL_lock *lock, MDL_key *key_arg)
+                                  void *_lock, const void *_key_arg)
   {
+    MDL_lock *lock= static_cast<MDL_lock *>(_lock);
+    const MDL_key *key_arg= static_cast<const MDL_key *>(_key_arg);
     DBUG_ASSERT(key_arg->mdl_namespace() != MDL_key::BACKUP);
     new (&lock->key) MDL_key(key_arg);
     if (key_arg->mdl_namespace() == MDL_key::SCHEMA)

sql/sql_show.cc

@@ -3789,7 +3789,7 @@ static bool show_status_array(THD *thd, const char *wild,
     */
     for (var=variables; var->type == SHOW_FUNC ||
            var->type == SHOW_SIMPLE_FUNC; var= &tmp)
-      ((mysql_show_var_func)(var->value))(thd, &tmp, buff,
+      ((mysql_show_var_func)(var->value))(thd, &tmp, (void *) buff,
                                           status_var, scope);
     
     SHOW_TYPE show_type=var->type;

sql/table_cache.cc

@@ -293,9 +293,11 @@ static void tc_remove_all_unused_tables(TDC_element *element,
         periodicly flush all not used tables.
 */
 
-static my_bool tc_purge_callback(TDC_element *element,
-                                 Share_free_tables::List *purge_tables)
+static my_bool tc_purge_callback(void *_element, void *_purge_tables)
 {
+  TDC_element *element= static_cast<TDC_element *>(_element);
+  Share_free_tables::List *purge_tables=
+      static_cast<Share_free_tables::List *>(_purge_tables);
   mysql_mutex_lock(&element->LOCK_table_share);
   tc_remove_all_unused_tables(element, purge_tables);
   mysql_mutex_unlock(&element->LOCK_table_share);
@@ -566,17 +568,20 @@ static void lf_alloc_destructor(uchar *arg)
 
 
 static void tdc_hash_initializer(LF_HASH *,
-                                 TDC_element *element, LEX_STRING *key)
+                                 void *_element, const void *_key)
 {
+  TDC_element *element= static_cast<TDC_element *>(_element);
+  const LEX_STRING *key= static_cast<const LEX_STRING *>(_key);
   memcpy(element->m_key, key->str, key->length);
   element->m_key_length= (uint)key->length;
   tdc_assert_clean_share(element);
 }
 
 
-static uchar *tdc_hash_key(const TDC_element *element, size_t *length,
+static uchar *tdc_hash_key(const unsigned char *_element, size_t *length,
                            my_bool)
 {
+  const TDC_element *element= (const TDC_element *) _element;
   *length= element->m_key_length;
   return (uchar*) element->m_key;
 }

storage/perfschema/ha_perfschema.cc

@@ -133,7 +133,9 @@ static int pfs_done_func(void *p)
   DBUG_RETURN(0);
 }
 
-static int show_func_mutex_instances_lost(THD *thd, SHOW_VAR *var, char *buff)
+static int show_func_mutex_instances_lost(THD *thd, SHOW_VAR *var, void *buff,
+                                          struct system_status_var *status_var,
+                                          enum enum_var_type)
 {
   var->type= SHOW_LONG;
   var->value= buff;