C语言中的undefined behavior系列(2)-- lifetime of object

文章的传送门: C语言中的undefined behavior/unspecified behavior - 序

嗷嗷的话: 本文里只要是大段大段的英文，都来至C99标准。所有的中文注释都是我对标准的理解。在文中使用的编译器是开了C99支持Intel C Compiler 11 for Windows.

— An object is referred tooutside of its lifetime (6.2.4).

— The value of a pointer to anobject whose lifetime has ended is used (6.2.4).

— The value of an object withautomatic storage duration is used while it is indeterminate (6.2.4, 6.7.8,6.8).

这三种undefined behavior是相当常见的问题。例如:

  
    

   
     
   
     char
   
     *
   
      fun(){
 
   
     char
   
      p[] 
   
     =
   
      
   
     "
   
     Is OK
   
     "
   
     ;
 
   
     return
   
      p; 
   
     //
   
     returning address of local variable or temporary
   
     

   
     }
 

   
     void
   
      func(){
 
   
     int
   
      
   
     *
   
     p 
   
     =
   
      NULL;
 {
 
   
     int
   
      k;
 k 
   
     =
   
      
   
     1
   
     ;
 p 
   
     =
   
      
   
     &
   
     k;
 }
 
   
     *
   
     p 
   
     =
   
      
   
     10
   
     ; 
   
     //
   
     refer to an object whose lifetime has ended
   
     

   
     }
 

   
     void
   
      fun1()
{
 
   
     int
   
      i;
 
   
     if
   
      (i 
   
     ==
   
      
   
     0
   
     ) 
   
     //
   
      uninitialized local variable 'i' used
   
     

   
      {
 }

}