Linux下指针NULL_0x0_指针为0x0

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
static int*p;
int main()
{
        printf("static no initial:\n");
        if(p==0)printf("p==0\n");
        if(p>0)printf("%s","p>0\n");
        if(p==NULL)printf("%s","p==NULL\n");
 
        printf("set p=0x0:\n");
         p=0x0;
        if(p==0)printf("%s","0x0==0\n");
        if(p>0)printf("%s","0x0>0\n");
        if(p==NULL)printf("%s","0x0==NULL\n");
 
//       指针无指向，段错误
//       printf("memset:\n");
//       memset(p,0,sizeof(int*));
//      if(p==0)printf("%s","memset==0\n");
//      if(p>0)printf("%s","memset>0\n");
//      if(p==NULL)printf("%s","memset==NULL\n");
 
//      指针无指向，段错误
//      printf("bzero:\n");
//       bzero(p,sizeof(p));
//      if(p==0)printf("%s","bzero==0\n");
//      if(p>0)printf("%s","bzero>0\n");
//      if(p==NULL)printf("%s","bzero==NULL\n");
 
         p=(int*)malloc(sizeof(int));
         printf("\nmemset:\n");
         memset(p,0,sizeof(int*));
        if(p==0)printf("%s","memset==0\n");
        if(p>0)printf("%s","memset>0\n");
        if(p==NULL)printf("%s","memset==NULL\n");
        if(0==*p)printf("*p==0\n");
        else if(*p>0)printf("*p>0\n");
 
 
        printf("\nbzero:\n");
         bzero(p,sizeof(p));
        if(p==0)printf("%s","bzero==0\n");
        if(p>0)printf("%s","bzero>0\n");
        if(p==NULL)printf("%s","bzero==NULL\n");
        if(0==*p)printf("*p==0\n");
        else if(*p>0)printf("*p>0\n");
 
        free(p);//与malloc成对使用
 
        p=NULL;
        return 0;
}

//结果
static no initial:
p==0
p==NULL
set p=0x0:
0x0==0
0x0==NULL
 
memset:
memset>0
*p==0
 
bzero:
bzero>0
*p==0