[kenel] add static name for rt_object (#6422)

增加静态object 名字，用户可以根据内存实际使用情况决定使用动态还是静态。适用于资源极度受限的情况下使用。该功能在RT-Thread完整版本中不常用，主要用于RT-Thread Nano，以缩减对内存的占用。由于没有动态拼接支持，在静态名字下，空闲线程的名字在多核时将命名成相同的名字。

src/Kconfig

@@ -3,11 +3,12 @@ menu "RT-Thread Kernel"
 
 config RT_NAME_MAX
     int "The maximal size of kernel object name"
-    range 2 32
+    range 0 64
     default 8
     help
         Each kernel object, such as thread, timer, semaphore etc, has a name,
         the RT_NAME_MAX is the maximal size of this object name.
+        If RT_NAME_MAX sets as 0, the name will be const.
 
 config RT_USING_ARCH_DATA_TYPE
     bool "Use the data types defined in ARCH_CPU"

src/idle.c

@@ -306,13 +306,21 @@ static void rt_thread_system_entry(void *parameter)
 void rt_thread_idle_init(void)
 {
     rt_ubase_t i;
+#if RT_NAME_MAX > 0
     char idle_thread_name[RT_NAME_MAX];
+#endif /* RT_NAME_MAX > 0 */
 
     for (i = 0; i < _CPUS_NR; i++)
     {
-        rt_sprintf(idle_thread_name, "tidle%d", i);
+#if RT_NAME_MAX > 0
+        rt_snprintf(idle_thread_name, RT_NAME_MAX, "tidle%d", i);
+#endif /* RT_NAME_MAX > 0 */
         rt_thread_init(&idle_thread[i],
+#if RT_NAME_MAX > 0
                 idle_thread_name,
+#else
+                "tidle",
+#endif /* RT_NAME_MAX > 0 */
                 idle_thread_entry,
                 RT_NULL,
                 &idle_thread_stack[i][0],

src/object.c

@@ -387,8 +387,11 @@ void rt_object_init(struct rt_object         *object,
     /* initialize object's parameters */
     /* set object type to static */
     object->type = type | RT_Object_Class_Static;
-    /* copy name */
-    rt_strncpy(object->name, name, RT_NAME_MAX);
+#if RT_NAME_MAX > 0
+    rt_strncpy(object->name, name, RT_NAME_MAX);  /* copy name */
+#else
+    object->name = name;
+#endif /* RT_NAME_MAX > 0 */
 
     RT_OBJECT_HOOK_CALL(rt_object_attach_hook, (object));
 
@@ -483,8 +486,11 @@ rt_object_t rt_object_allocate(enum rt_object_class_type type, const char *name)
     /* set object flag */
     object->flag = 0;
 
-    /* copy name */
-    rt_strncpy(object->name, name, RT_NAME_MAX);
+#if RT_NAME_MAX > 0
+    rt_strncpy(object->name, name, RT_NAME_MAX); /* copy name */
+#else
+    object->name = name;
+#endif /* RT_NAME_MAX > 0 */
 
     RT_OBJECT_HOOK_CALL(rt_object_attach_hook, (object));