two .h file is call each other, and causes compilation to fail

in stack_tree.h, i need to use TreeNode*,but it is defined in tree.h, so i try to include “tree.h”,just like the following code:

stack_tree.h:
#include "tree.h"
#define variable_type TreeNode*
#define MaxSize 50

typedef struct stack
{
    variable_type data[MaxSize];
    int top;
}SqStack;   //栈的顺序存储

but in tree.h , i need to use SqStack, so i have to include “stack_tree.h”,This causes the two h files to include each other，then compile is false

tree.h:
typedef struct tree
{
    int val;
    struct tree *lnext;
    struct tree *rnext;
    SqStack* next;
}TreeNode;

how can i solve this problem?