c - two structs that refer to each other

Question

How can I have two different structs that refer to each other? One holds a pointer to the other and I also have a forward declaration:

struct json_array_t; 

struct json_array_entry_t {
    enum json_type type;                
    union {
        bool                boolean; 
        long long           integer; 
        double              floating; 
        char*               string; 
        struct json_array_t array; 
    }; 
}; 

struct json_array_t {
    struct json_array_entry_t* entries; 
    size_t len, cap;
};

I am getting these errors:

error: field ‘array’ has incomplete type
   27 |         struct json_array_t array;

Answer 1

You must first define struct json_array_t and then struct json_array_entry_t.

When you now define in struct json_array_entry_t an occurrence of json_array_t it and all its members are fully known to the compiler.