c++ - 双链表实现中的"Conditional jump or move depends on uninitialised value"

Question

Valgrind 告诉我两个我无法解决的错误。我在以下函数 unplug_set 中收到“条件跳转或移动取决于未初始化的值”错误消息。是因为 NULL 检查吗？该函数应该从双链表中拔出元素。

void unplug_set(set * set_to_unplug){
        set * last_set = set_to_unplug->last;
        set * next_set = set_to_unplug->next;
        set_to_unplug->next = NULL;
        set_to_unplug->last = NULL;
148     if(last_set == NULL && next_set == NULL){ // only one element left
          ordered_by_score_set[set_to_unplug->weight] = NULL;
150     }else if(last_set == NULL){ // first set
          next_set->last = NULL;
          ordered_by_score_set[set_to_unplug->weight] = next_set;
        } else if (next_set == NULL) { // last set
          last_set->next = NULL;
        } else { // set in the middle
          last_set->next = next_set;
        next_set->last = last_set;
       }
}

Valgrind 命令:

valgrind --dsymutil=yes --track-origins=yes ./set_program

输出:

==45085== Conditional jump or move depends on uninitialised value(s)
==45085==    at 0x100001A2C: unplug_set(set*) (:148)
                          ...
==45085==    by 0x100001294: main (Main.cpp:81)
==45085==  Uninitialised value was created by a heap allocation
==45085==    at 0xC713: malloc (vg_replace_malloc.c:274)
==45085==    by 0x63346: operator new(unsigned long) (in /usr/lib/libstdc++.6.0.9.dylib)
==45085==    by 0x100001E0C: add_set(int, int, unsigned int const*, unsigned short const*, int, unsigned int const*) (:57)
==45085==    by 0x10000127E: main (Main.cpp:39)
==45085==
==45085== Conditional jump or move depends on uninitialised value(s)
==45085==    at 0x100001A60: unplug_set(set*) (:150)
                          ...
==45085==    by 0x100001294: main (Main.cpp:81)
==45085==  Uninitialised value was created by a heap allocation
==45085==    at 0xC713: malloc (vg_replace_malloc.c:274)
==45085==    by 0x63346: operator new(unsigned long) (in /usr/lib/libstdc++.6.0.9.dylib)
==45085==    by 0x100001E0C: add_set(int, int, unsigned int const*, unsigned short const*, int, unsigned int const*) (:57)
==45085==    by 0x10000127E: main (Main.cpp:39)

Answer 1

set_to_unplug 参数值由其构造函数使用 new 运算符初始化。如果构造函数中没有初始化，那么你就有了 valgrind 提示的原因。

我们没有足够的信息来回答您的问题。发布如何使用此功能。以及如何初始化参数值。