问题通过 c 中的方法/函数传递结构

Question

I am having issues with the following method. It supposed to change the value of mq.queue[qCounter].id to that found in ident and it does this but the value is not retained outside after the method is done. It only seems to change while in the method. I tried de-referencing the attribute mq but and there were no compilation errors but the program stopped running whenever it got to the method. Any ideas how I can fix it/ achieve the same thing using a method/function?

void createQ(MsgQs_t mq, int ident){
    int taken=0;
    for(int i=0;i<3;i++){
        if(mq.queue[i].id==ident){
            printf("That Queue Id is already taken\n");
            taken=1;
        }
    }
    if(taken==0){
    mq.queue[qCounter].id=ident;
    printf("THE INNER ID IS %d and the qCounter is %d\n", mq.queue[qCounter].id, qCounter);
    qCounter++;
    }
}

The following is the struct im using aka "MsgQs mq" above:

typedef struct MessQ {//A single message queue
    char message[MQS][MLN];
    int id;
}MessQ_t;

typedef struct MsgQs {//An array of message queues
    MessQ_t queue[MQA];
}MsgQs_t;

Answer 1

In function createQ argument MsgQs_t mq used as pass-by-value and hence caller component will not have any changes upon editing in mq

Change code to pass-by-reference something like,

 void createQ(MsgQs_t *mq, int ident){
//                    ^^^^^^ Here
        int taken=0;
        for(int i=0;i<3;i++){
            if(mq->queue[i].id==ident){
  //           ^^^^^^ Here change dot(.) to this (->) for access
                    printf("That Queue Id is already taken\n");
                    taken=1;
                }
            }
            if(taken==0){
            mq->queue[qCounter].id=ident;
            printf("THE INNER ID IS %d and the qCounter is %d\n", mq->queue[qCounter].id, qCounter);
            qCounter++;
            }
        }

While calling the function send the address as follows,

createQ(&mq, indent_value);