MDEV-28762: recursive call of some json functions without stack control

Fixup to MDEV-28762. Fixes warnings about unused variable "stack_used_up"
during building with RelWithDebInfo

sql/item_jsonfunc.cc

@@ -1243,10 +1243,12 @@ static int check_contains(json_engine_t *js, json_engine_t *value)
 {
   json_engine_t loc_js;
   bool set_js;
-  long arbitrary_var;
-  long stack_used_up= (available_stack_size(current_thd->thread_stack, &arbitrary_var));
   DBUG_EXECUTE_IF("json_check_min_stack_requirement",
-                  {ALLOCATE_MEM_ON_STACK(my_thread_stack_size-stack_used_up-STACK_MIN_SIZE);});
+                  {
+                    long arbitrary_var;
+                    long stack_used_up= (available_stack_size(current_thd->thread_stack, &arbitrary_var));
+                    ALLOCATE_MEM_ON_STACK(my_thread_stack_size-stack_used_up-STACK_MIN_SIZE);
+                  });
   if (check_stack_overrun(current_thd, STACK_MIN_SIZE , NULL))
     return 1;
 
@@ -2238,10 +2240,12 @@ String *Item_func_json_object::val_str(String *str)
 static int do_merge(String *str, json_engine_t *je1, json_engine_t *je2)
 {
 
-  long arbitrary_var;
-  long stack_used_up= (available_stack_size(current_thd->thread_stack, &arbitrary_var));
   DBUG_EXECUTE_IF("json_check_min_stack_requirement",
-                  {ALLOCATE_MEM_ON_STACK(my_thread_stack_size-stack_used_up-STACK_MIN_SIZE);});
+                  {
+                    long arbitrary_var;
+                    long stack_used_up= (available_stack_size(current_thd->thread_stack, &arbitrary_var));
+                    ALLOCATE_MEM_ON_STACK(my_thread_stack_size-stack_used_up-STACK_MIN_SIZE);
+                  });
   if (check_stack_overrun(current_thd, STACK_MIN_SIZE , NULL))
     return 1;
 
@@ -2579,10 +2583,12 @@ static int copy_value_patch(String *str, json_engine_t *je)
 static int do_merge_patch(String *str, json_engine_t *je1, json_engine_t *je2,
                           bool *empty_result)
 {
-  long arbitrary_var;
-  long stack_used_up= (available_stack_size(current_thd->thread_stack, &arbitrary_var));
   DBUG_EXECUTE_IF("json_check_min_stack_requirement",
-                  {ALLOCATE_MEM_ON_STACK(my_thread_stack_size-stack_used_up-STACK_MIN_SIZE);});
+                  {
+                    long arbitrary_var;
+                    long stack_used_up= (available_stack_size(current_thd->thread_stack, &arbitrary_var));
+                    ALLOCATE_MEM_ON_STACK(my_thread_stack_size-stack_used_up-STACK_MIN_SIZE);
+                  });
   if (check_stack_overrun(current_thd, STACK_MIN_SIZE , NULL))
     return 1;
 
@@ -4567,10 +4573,12 @@ int json_find_overlap_with_object(json_engine_t *js, json_engine_t *value,
 */
 int check_overlaps(json_engine_t *js, json_engine_t *value, bool compare_whole)
 {
-  long arbitrary_var;
-  long stack_used_up= (available_stack_size(current_thd->thread_stack, &arbitrary_var));
   DBUG_EXECUTE_IF("json_check_min_stack_requirement",
-                  {ALLOCATE_MEM_ON_STACK(my_thread_stack_size-stack_used_up-STACK_MIN_SIZE);});
+                  {
+                    long arbitrary_var;
+                    long stack_used_up= (available_stack_size(current_thd->thread_stack, &arbitrary_var));
+                    ALLOCATE_MEM_ON_STACK(my_thread_stack_size-stack_used_up-STACK_MIN_SIZE);
+                  });
   if (check_stack_overrun(current_thd, STACK_MIN_SIZE , NULL))
     return 1;
 

sql/json_table.cc

@@ -118,10 +118,12 @@ int get_disallowed_table_deps_for_list(MEM_ROOT *mem_root,
   NESTED_JOIN *nested_join;
   List_iterator<TABLE_LIST> li(*join_list);
 
-  long arbitrary_var;
-  long stack_used_up= (available_stack_size(current_thd->thread_stack, &arbitrary_var));
   DBUG_EXECUTE_IF("json_check_min_stack_requirement",
-                  {ALLOCATE_MEM_ON_STACK(my_thread_stack_size-stack_used_up-STACK_MIN_SIZE);});
+                  {
+                    long arbitrary_var;
+                    long stack_used_up= (available_stack_size(current_thd->thread_stack, &arbitrary_var));
+                    ALLOCATE_MEM_ON_STACK(my_thread_stack_size-stack_used_up-STACK_MIN_SIZE);
+                  });
   if (check_stack_overrun(current_thd, STACK_MIN_SIZE , NULL))
     return 1;
 
@@ -1344,13 +1346,14 @@ static void add_extra_deps(List<TABLE_LIST> *join_list, table_map deps)
   TABLE_LIST *table;
   List_iterator<TABLE_LIST> li(*join_list);
 
-  long arbitrary_var;
-  long stack_used_up= (available_stack_size(current_thd->thread_stack, &arbitrary_var));
   DBUG_EXECUTE_IF("json_check_min_stack_requirement",
-                  {ALLOCATE_MEM_ON_STACK(my_thread_stack_size-stack_used_up-STACK_MIN_SIZE);});
+                  {
+                    long arbitrary_var;
+                    long stack_used_up= (available_stack_size(current_thd->thread_stack, &arbitrary_var));
+                    ALLOCATE_MEM_ON_STACK(my_thread_stack_size-stack_used_up-STACK_MIN_SIZE);
+                  });
   if (check_stack_overrun(current_thd, STACK_MIN_SIZE , NULL))
     return;
-
   while ((table= li++))
   {
     table->dep_tables |= deps;
@@ -1439,10 +1442,12 @@ table_map add_table_function_dependencies(List<TABLE_LIST> *join_list,
   table_map res= 0;
   List_iterator<TABLE_LIST> li(*join_list);
 
-  long arbitrary_var;
-  long stack_used_up= (available_stack_size(current_thd->thread_stack, &arbitrary_var));
   DBUG_EXECUTE_IF("json_check_min_stack_requirement",
-                  {ALLOCATE_MEM_ON_STACK(my_thread_stack_size-stack_used_up-STACK_MIN_SIZE);});
+                  {
+                    long arbitrary_var;
+                    long stack_used_up= (available_stack_size(current_thd->thread_stack, &arbitrary_var));
+                    ALLOCATE_MEM_ON_STACK(my_thread_stack_size-stack_used_up-STACK_MIN_SIZE);
+                  });
   if ((res=check_stack_overrun(current_thd, STACK_MIN_SIZE , NULL)))
     return res;