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
    {
    }

}