避免堆损坏

Question

今天,在文章堆损坏的 EFNet C++ Wiki上,我找到了两段代码.

void this_is_bad() /* You wouldn't believe how often this kind of code can be found */    
{    
    char *p = new char[5];    /* spend some cycles in the memory manager */    
    /* do some stuff with p */    
    delete[] p;      /* spend some more cycles, and create an opportunity for a leak */    
 }  

替代方式:

void this_is_good()    
{    
   /* Avoid allocation of small temporary objects on the heap*/   
   char p[5];    /* Use the stack instead */   
   /* do some stuff */  
}    

有人可以帮助我理解为什么第一段代码不被认为是好的吗？

Answer 1

在使用时char* p,您在p堆上进行分配,因此您必须在最后处理它.之间的char *p和delete,在do some stuff with p中,代码可能抛出一个异常,p被泄露.

在使用时char p[5],你在p堆栈上分配你不需要处理的方式delete,即使代码抛出异常,你也是安全的.

void this_is_bad()   
{    
  char *p = new char[5]; //on the heap
  // What happens if I throw an unhandled exception here?
  delete[] p;  // I never get to delete p and it gets leaked
}