c - 无法定位 "dereferencing pointer to incomplete type"错误的来源

Question

作为大学类(class)作业的一部分，我需要用 C(不是 C++)编写一个 CPU 调度模拟器。我在使用 GCC 编译时遇到了一个问题，它给了我几个关于“取消引用指向不完整类型的指针”的错误。所有错误都是同一代码的结果，这让我认为该代码存在问题。

违规代码是:

//Push a record of this state change to the back of the simulation's history list
listPushBack(sim->history, (void*)newRecord(p->pid, sim->currentTime, wait, ready));

这与跟踪模拟历史以供稍后分析有关。记录定义为:

//History.h

typedef struct record* Record;

//History.c

typedef struct record recordType;

struct record{
    long time;
    int pid;
    State oldState;
    State newState;
};

Record newRecord(int pid, long time, ProcessState oldState, ProcessState newState){
    Record r = (Record)malloc(sizeof(recordType));
    if(r == NULL){
        fprintf(stderr, "History.c:newRecord:Failed to allocate memory for new Record\n");
        //This is serious, abort execution
        exit(-1)
    }
    r->time = time;
    r->pid = pid;
    r->oldState = oldState;
    r->newState = newState;
    return r;
}

其中 ProcessState 定义为:

//Process.h

typedef enum process_state ProcessState;

enum process_state{
    arrive = 0,
    ready = 1,
    run = 2,
    wait = 3,
    done = 4
};

我玩了一下，得到了同样的错误:

Process p = (Process)listGetAt(sim->waitingQueue, i);
ProcessState old = p->state;
listPushBack(sim->history, (void*)newRecord(p->pid, sim->currentTime, old, p->state));

谢天谢地，这不会再过一个星期，所以我有时间玩，但我希望有人能在我浪费太多时间搞砸之前给我指明正确的方向。

编辑:按评论中出现的顺序回答问题，

//DoubleLinkList.c

bool listPushBack(DoubleList l, void* data){
    return listInsert(l, data, -1);
}
bool listInsert(DoubleList l, void* data, int pos){
    int index = pos;
    //If value is negative, convert to a index relative to the end of the list
    if(index < 0){
        index = listSize(l) + index + 1;
    }
    //Check index bounds
    if(index > listSize(l) || index < 0){
        fprintf(stderr, "DoubleLinkList.c:listInsert:Insert index %i out of bounds\n", pos);
        //This is not serious enough to warrent an abort
        return false;
    }
    //Data is null
    if(data == NULL){
        fprintf(stderr, "DoubleLinkList.c:listInsert:Data value for doubly linked list node cannot be NULL\n");
        //This is not serious enough to warrent an abort
        return false;
    }
    Node insertNode = newNode(data);
    //Case: End of list
    if(index == listSize(l)){
        l->tail->next = insertNode;
        insertNode->prev = l->tail;
        l->tail = insertNode;
        l->size++;
        return true;
    }
    //Case: Start of list
    else if(index == 0){
        l->head->prev = insertNode;
        insertNode->next = l->head;
        l->head = insertNode;
        l->size++;
        return true;
    }
    //Case: Middle of list
    Node node = l->head;
    //Scan through list to reach index pos
    int i;
    for(i = 0; i < index; i++){
        if(node == NULL){
            fprintf(stderr, "DoubleLinkList.c:listGetPosition:NULL encoutered unexpectedly while traversing doubly linked list at index %i\n", i);
            //This is a serious problem, abort execution
            exit(-1);
        }
        node = node->next;
    }
    //Insert before Node at index pos
    insertNode->next = node;
    insertNode->prev = node->prev;
    node->prev->next = insertNode;
    node->prev = insertNode;
    l->size++;
    return true;
}

是的，过程是:

typedef process_Struct* Process

模拟声明:

//Simulation.c
struct simulation{
    SimType type;
    long currentTime;
    unsigned int totalProcesses;
    DoubleList arriveQueue;
    DoubleList readyQueue;
    DoubleList waitingQueue;
    DoubleList doneQueue;
    Process running;
    DoubleList history;
};

抛出问题的方法是 runSimulation(Simulation sim) 其中:

typedef simulation* Simulation;

runSimulation 在 Simulation.c 中声明

确切的错误信息是:source/Simulation.c:154:50: error: dereferencing pointer to incomplete type这就是为什么这被证明如此烦人，它没有提供任何更多信息，即使使用 -verbose、-g 和其他一些调试标志也是如此。

我意识到我不应该使用 typdef 指针，但是，愚蠢的是，教授将其作为作业的要求。去引用:“如果可能，使用 typedef 来定义指向结构的指针。这样 TA 就可以更轻松地阅读您的模拟代码。”我对此非常恼火，因为这是一个糟糕的主意，助教应该能够阅读代码。

Answer 1

您的评论表明您正在 history.c 源文件中定义 struct record。如果您在任何其他源文件中使用 struct record，那么您应该在 history.h 中定义它，否则当您尝试使用指向另一个文件中的 struct record 的指针。