這段代碼會做什麼？ （內存管理）

Question

char *p = new char[200]; 
char *p1 = p; 
char *p2 = &p[100]; 
delete [] p1; 

順便說一句，這不是測試或任何我真正需要知道這一點:)

Answer 1

// allocate memory for 200 chars 
// p points to the begining of that 
// block 
char *p = new char[200]; 
// we don't know if allocation succeeded or not 
// no null-check or exception handling 

// **Update:** Mark. Or you use std::no_throw or set_new_handler. 
// what happens next is not guranteed 

// p1 now points to the same location as p 
char *p1 = p; 

// another pointer to char which points to the 
// 100th character of the array, note that 
// this can be treated as a pointer to an array 
// for the remaining 100-odd elements 
char *p2 = &p[100]; 

// free the memory for 200 chars 
delete [] p1; 

// **Update:** Doug. T 
// [...] p and p2 are now pointing to freed memory 
// and accessing it will be undefined behavior 
// depending on the executing environment.