数组类型具有不完整的元素类型“结构指令”

Question

How do I make this struct instruction visible to struct cpu state? Like If I put cpu state struct first it doesn't work because some other arguments won't be visible to struct instruction but if I put it reverse again I have a problem.

struct  cpu_state
{
    int nextinstructionlinenumber;
    char filename[200];
    char RLO;

    struct instruction instructionlist[INSTRUCTIONLIST_SIZE];
    int instructionlistnumber;
    struct variable variablelist[INSTRUCTIONLIST_SIZE];
    int variablelistnumber;

};
struct cpu_state CPU; 


struct instruction{
    char name[LINE_CHAR_NUM];
    void(*function)(struct cpu_state* pstate, struct line* pline);
};

Answer 1

You can create incomplete structure declarations provided they are just used for pointers. For example, the following order will work. Note that I created a dummy definition for struct variable since it was absent from the post. You can replace it with whatever you like:

struct variable {
    int     dummy_val;
};

struct cpu_state;
struct line;

struct instruction{
    char name[LINE_CHAR_NUM];
    void(*function)(struct cpu_state* pstate, struct line* pline);
};

struct  cpu_state
{
    int nextinstructionlinenumber;
    char filename[200];
    char RLO;

    struct instruction instructionlist[INSTRUCTIONLIST_SIZE];
    int instructionlistnumber;
    struct variable variablelist[INSTRUCTIONLIST_SIZE];
    int variablelistnumber;

};

struct cpu_state CPU;