C语言void*和*p的使用

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <time.h>
#include <pthread.h>
#include <semaphore.h>
#include <unistd.h>
#include <signal.h>
#include <string.h>
#include <stdlib.h>

#define USB_CLASS_VIDEO 0x0e
#define UVC_SC_VIDEO_INTERFACE_COLLECTION  0x03
#define UVC_INTF_VIDEO_CONTROL   0
#define USB_DT_INTERFACE_ASSOCIATION 0x0b

typedef __signed__ char __s8;
typedef unsigned char __u8;

typedef __signed__ short __s16;
typedef unsigned short __u16;

typedef __signed__ int __s32;
typedef unsigned int __u32;


/* USB_DT_INTERFACE_ASSOCIATION: groups interfaces */
struct usb_interface_assoc_descriptor {
	__u8  bLength;
	__u8  bDescriptorType;

	__u8  bFirstInterface;
	__u8  bInterfaceCount;
	__u8  bFunctionClass;
	__u8  bFunctionSubClass;
	__u8  bFunctionProtocol;
	__u8  iFunction;
} __attribute__ ((packed));



static struct usb_interface_assoc_descriptor uvc_iad = {
	.bLength = sizeof(uvc_iad),
	.bDescriptorType = USB_DT_INTERFACE_ASSOCIATION,
	.bFirstInterface = 0,
	.bInterfaceCount = 2,
	.bFunctionClass = USB_CLASS_VIDEO,
	.bFunctionSubClass = UVC_SC_VIDEO_INTERFACE_COLLECTION,
	.bFunctionProtocol = 0x00,
	.iFunction = 0,
};

//0-8 ?
int main()
{

    struct usb_interface_assoc_descriptor* puvc_iad = NULL;
    puvc_iad = &uvc_iad;

    printf("  sizeof %d  \n",sizeof(*puvc_iad));
    printf("p is sizeof %d\n",sizeof(void*));




    for(;;);
    return 0;
}