运行结构并打印所有值？

Question

我有一个指向结构的指针,我想通过反复试验获取所有成员.我试图通过将指针递增1并对其进行解除来完成结构.它应该从结构中返回一个正确的值(每次i*sizeof(int)),但它不会.

我究竟做错了什么？

fn (mach_msg_header_t *InHeadP, mach_msg_header_t *OutHeadP)
{

    /*
     assume that all struct members are int types

     typedef    struct 
     {
     mach_msg_bits_t    msgh_bits;
     mach_msg_size_t    msgh_size;
     mach_port_t        msgh_remote_port;
     mach_port_t        msgh_local_port;
     mach_msg_size_t    msgh_reserved;
     mach_msg_id_t      msgh_id;
     } mach_msg_header_t;

     size of the struct is 24.
     */

    printf("ID: %d \n",InHeadP->msgh_id); //prints 'ID: 1337'
    printf("Ptr: %p\n",InHeadP);

    for (int i = 0; i <= 24; i++)
    {
        int deref = *((int*)(InHeadP+i));
        printf("InHeadP[%d]=%d\n",i,deref);
            //no sign of 1337 anywhere

    }
}

PS我知道我不应该这样做,但这仅用于测试目的.

Answer 1

因为InHeadP是a mach_msg_header_t*,向它添加一个整数实际上会添加整数倍sizeof(mach_msg_header_t),就好像你索引一个mach_msg_header_ts 数组(实际上是数组索引的工作原理).你需要转换InHeadP到int* 之前在其上进行运算,即使如此,与结构有六个字段,i只应上升到6,而不是24.