传递指针参数（函数内部给指针赋值）示例

#include <stdio.h>

unsigned char *ptr = NULL;
unsigned char num = 3;

static void fun(unsigned char **mem)
{
    *mem = &num;    
} 

int main()
{
    fun(&ptr);
    printf("%d \n", *ptr);
    
    return 0;
}