#include <stdio.h>
/* using sizeof long int */
int word_size()
{
void *p;
return sizeof(p); /* the length of pointer */
}
/* using pointer */
int word_size()
{
void **ptr;
// 这里如果没用强制类型转换（unsigned long），编译器就会优化这个语句成：ptr+1-ptr，结果就成1了
return ((unsigned long)(ptr+1)-(unsigned long)(ptr)); /* the length of pointer variable */
}
int main()
{
printf("The size of machine word is %d\n", word_size());
}