shell: Allocate proper amount of history slab memory

include/shell/shell.h

@@ -493,7 +493,7 @@ extern void shell_print_stream(const void *user_ctx, const char *data,
 	SHELL_LOG_BACKEND_DEFINE(_name, _name##_out_buffer,		      \
 				 CONFIG_SHELL_PRINTF_BUFF_SIZE,		      \
 				 _log_queue_size, _log_timeout);	      \
-	SHELL_HISTORY_DEFINE(_name, 128, 8);/*todo*/			      \
+	SHELL_HISTORY_DEFINE(_name, CONFIG_SHELL_CMD_BUFF_SIZE, 7);	      \
 	SHELL_FPRINTF_DEFINE(_name##_fprintf, &_name, _name##_out_buffer,     \
 			     CONFIG_SHELL_PRINTF_BUFF_SIZE,		      \
 			     true, shell_print_stream);			      \

include/shell/shell_history.h

@@ -22,11 +22,19 @@ struct shell_history {
 	sys_dlist_t list;
 	sys_dnode_t *current;
 };
+
+struct shell_history_item {
+	sys_dnode_t dnode;
+	u16_t len;
+	char data[];
+};
+
 #if CONFIG_SHELL_HISTORY
 #define SHELL_HISTORY_DEFINE(_name, block_size, block_count)	\
 								\
 	K_MEM_SLAB_DEFINE(_name##_history_memslab,		\
-			  block_size, block_count, 4);		\
+		 ROUND_UP(block_size + sizeof(struct shell_history_item), \
+			  sizeof(void *)), block_count, 4);		\
 	static struct shell_history _name##_history = {		\
 		.mem_slab = &_name##_history_memslab		\
 	}

subsys/shell/shell_history.c

@@ -7,12 +7,6 @@
 #include <shell/shell_history.h>
 #include <string.h>
 
-struct shell_history_item {
-	sys_dnode_t dnode;
-	u16_t len;
-	char data[1];
-};
-
 void shell_history_mode_exit(struct shell_history *history)
 {
 	history->current = NULL;