malloc(0)

char * ptr;
ptr=(char*)malloc(0);
if(ptr==NULL)
{
cout<<"it is a null pointer"<<endl;

}
else
{
cout<<"it is a non-null pointer"<<endl;
cout<<"the length is "<<sizeof(ptr)<<endl;
cout<<"the strlen is "<<strlen(ptr)<<endl;
}


输出结果：it is a non-null pointer
                the length is 4
                the strlen is 16
把0传给malloc，可以得到一个合法的指针。