117.笔试中常考到的指针问_txt.txt

总结了一些软硬件方面的笔试面试题

笔试中常考到的指针问题ZZ 
shury 发表于 2004-12-9 15:12:00 

＃i nclude <iostream> 
＃i nclude <malloc.h> 
using namespace std; 

void GetMemory(char *p,int num) 
{ 
p=(char*)malloc(sizeof(char)*num); 
} 

void test(void) 
{ 
char* str=NULL; 
GetMemory(str,100); //str仍然为NULL 
strcpy(str,"hello");     //运行错误 
} 

void GetMemory2(char **p,int num) 
{ 
*p=(char*)malloc(sizeof(char)*num); 
} 

void test2(void) 
{ 
char *str=NULL; 
GetMemory2(&str,100); 
strcpy(str,"hello"); 
cout<<str<<endl; 
free(str); 
} 

char *GetMemory3(int num) 
{ 
char* p=(char*)malloc(sizeof(char)*num); 
return p; 
} 

void test3(void) 
{ 
char* str=NULL; 
str=GetMemory3(100); 
strcpy(str,"hello"); 
cout<<str<<endl; 
free(str); 
} 

char* GetString(void) 
{ 
char p[]="hello world";    //位于堆栈内存 
return p; 
} 

void test4(void) 
{ 
char* str=NULL; 
str=GetString();        //str的内容是垃圾 
cout<<str<<endl; 
} 

void main(void) 
{ 
// test();      
// test2(); 
// test3(); 
test4(); 
}