MDEV-23766: fix by assert (Windows)

sql/my_json_writer.h

@@ -24,7 +24,7 @@
 #ifdef JSON_WRITER_UNIT_TEST
 #include "sql_string.h"
 // Also, mock objects are defined in my_json_writer-t.cc
-#define VALIDITY_ASSERT(x) if ((!x)) this->invalid_json= true;
+#define VALIDITY_ASSERT(x) if (!(x)) this->invalid_json= true;
 #else
 #include "sql_select.h"
 #define VALIDITY_ASSERT(x) DBUG_ASSERT(x)
@@ -356,6 +356,9 @@ class Json_value_helper
 /* A common base for Json_writer_object and Json_writer_array */
 class Json_writer_struct
 {
+  Json_writer_struct(const Json_writer_struct&)= delete;
+  Json_writer_struct& operator=(const Json_writer_struct&)= delete;
+
 protected:
   Json_writer* my_writer;
   Json_value_helper context;
@@ -394,18 +397,15 @@ class Json_writer_object : public Json_writer_struct
     my_writer->add_member(name);
   }
 public:
-  explicit Json_writer_object(THD *thd)
-  : Json_writer_struct(thd)
-  {
-    if (unlikely(my_writer))
-      my_writer->start_object();
-  }
-
-  explicit Json_writer_object(THD* thd, const char *str)
+  explicit Json_writer_object(THD* thd, const char *str= nullptr)
     : Json_writer_struct(thd)
   {
     if (unlikely(my_writer))
-      my_writer->add_member(str).start_object();
+    {
+      if (str)
+        my_writer->add_member(str);
+      my_writer->start_object();
+    }
   }
 
   ~Json_writer_object()

sql/opt_range.cc

@@ -5101,9 +5101,8 @@ TABLE_READ_PLAN *get_best_disjunct_quick(PARAM *param, SEL_IMERGE *imerge,
                                              n_child_scans)))
     DBUG_RETURN(NULL);
 
-  Json_writer_object trace_best_disjunct = named_trace
-      ? Json_writer_object(thd, "best_disjunct_quick")
-      : Json_writer_object(thd);
+  const char* trace_best_disjunct_obj_name= named_trace ? "best_disjunct_quick" : nullptr;
+  Json_writer_object trace_best_disjunct(thd, trace_best_disjunct_obj_name);
   Json_writer_array to_merge(thd, "indexes_to_merge");
   /*
     Collect best 'range' scan for each of disjuncts, and, while doing so,
@@ -5649,7 +5648,7 @@ void print_keyparts(THD *thd, KEY *key, uint key_parts)
   DBUG_ASSERT(thd->trace_started());
 
   KEY_PART_INFO *part= key->key_part;
-  Json_writer_array keyparts= Json_writer_array(thd, "keyparts");
+  Json_writer_array keyparts(thd, "keyparts");
   for(uint i= 0; i < key_parts; i++, part++)
     keyparts.add(part->field->field_name);
 }