学步园

#include <iostream.h><br /> void fun0(int* p)<br /> {<br /> int* a=new int[3];<br /> *a=0;<br /> *(a+1)=1;<br /> *(a+2)=2;<br /> p=a;<br /> }</p> <p>void fun1(int* &p)<br /> {<br /> int* a=new int[3];<br /> *a=0;<br /> *(a+1)=1;<br /> *(a+2)=2;<br /> p=a;<br /> }</p> <p>void fun2(int* p)<br /> {<br /> *p=0;<br /> *(p+1)=1;<br /> *(p+2)=2;<br /> }</p> <p>//warning:returning address of local variable or temporary<br /> int* fun3()<br /> {<br /> int a[]={1,2,3};<br /> return a;<br /> }</p> <p>//warning C4172: returning address of local variable or temporary<br /> int*& fun4()<br /> {<br /> int* a=new int[3];<br /> a[0]=0;<br /> a[1]=1;<br /> a[2]=2;<br /> return a;<br /> }</p> <p>void fun5(int* p[3])<br /> {<br /> *p[0]=0; *(p[0]+1)=10;<br /> *p[1]=1; *(p[1]+1)=11;<br /> *p[2]=2; *(p[2]+1)=12;<br /> }</p> <p>//cannot convert from 'int [3]' to 'int *&<br /> /*<br /> int*& fun6()<br /> {<br /> int a[]={1,2,3};<br /> return a;<br /> }<br /> */</p> <p>void main()<br /> {<br /> int* p=new int[3];<br /> // int* p; //runtime error:the memory connot be written<br /> //it is necessory to allocate memory<br /> cout<<"test: void fun0(int* p)"<<endl;<br /> fun0(p);<br /> for(int i=0;i<3;i++){<br /> cout<<*(p+i)<<endl;<br /> }<br /> delete[3] p;</p> <p> p=new int[3];<br /> cout<<endl<<"test: void fun1(int* &p)"<<endl;<br /> fun1(p);<br /> for(i=0;i<3;i++){<br /> cout<<*(p+i)<<endl;<br /> }<br /> delete[3] p;</p> <p> p=new int[3];<br /> cout<<endl<<"test: void fun2(int* p)"<<endl;<br /> cout<<" allocate memory for the parameter"<<endl;<br /> fun2(p);<br /> for(i=0;i<3;i++){<br /> cout<<" "<<*(p+i)<<endl;<br /> }<br /> cout<<" donot allocate memory for the parameter"<<endl;<br /> cout<<" memory connot be written"<<endl;<br /> /*<br /> int* pt;<br /> fun2(pt); //runtime error:memory connot be written<br /> for(i=0;i<3;i++){<br /> cout<<*(pt+i)<<endl;<br /> }<br /> */<br /> delete[3] p;</p> <p> p=new int[3];<br /> cout<<endl<<"test: int* fun3()"<<endl;<br /> cout<<" debug assertion failed"<<endl;<br /> /*<br /> p=fun3(); //debug assertion failed<br /> for(i=0;i<3;i++){<br /> cout<<*(p+i)<<endl;<br /> }<br /> */<br /> delete[3] p;</p> <p> p=new int[3];<br /> cout<<endl<<"test: int*& fun4()"<<endl;<br /> p=fun4();<br /> for(i=0;i<3;i++){<br /> cout<<*(p+i)<<endl;<br /> }</p> <p>// delete[3] p;//??? Debug assertion failed</p> <p> cout<<endl<<"test: void fun5(int* p[3])"<<endl;<br /> int* p2[3];<br /> //it's necessory to allocate memory<br /> for(i=0;i<3;i++){<br /> p2[i]=new int[2];<br /> }<br /> fun5(p2);<br /> for(i=0;i<3;i++){<br /> cout<<*p2[i]<<" "<<*(p2[i]+1)<<endl;<br /> }</p> <p> delete[6] *p2; //also right in this form<br /> // delete[2] p2[0];<br /> // delete[2] p2[1];<br /> // delete[2] p2[2];<br /> }