C ++ STL列表函数使用空列表进行segfault [英] C++ STL list functions segfaulting with empty list

问题描述

我有一个指针列表作为类的成员。我实例化那个类，并且当列表为空时，诸如size（）和empty（）的各种函数会失败并显示segfault。当我添加的东西到列表中，他们很好。我试图抽象我在做一个测试文件，它的工作完美。这是我想我当我的代码失败时（虽然显然不是）：

I have a list of pointers as a member of a class. I instantiate that class, and various functions such as size() and empty() fail with a segfault when the list is empty. When I add something to the list, they're fine. I tried to abstract what I'm doing with a test file, and it works perfectly. This is what I THINK I'm doing when my code fails (though am clearly not):

#include <list>
#include <iostream>

class Test {
  int i;
};

int main() {
  std::list<Test*> tlist;

  if (tlist.empty()) {
    std::cout << "List empty";
  } else {
    std::cout << "List not empty";
  }
}

我不能真正发布整个代码清单导致的问题，因为它是相当大的和一堆文件，但会尝试直接粘贴所有相关的代码：

I can't really post the entire code listing that's causing the issue, as it's fairly large and over a bunch of files, but will try to paste all the relevant bits straight from code:

播放器中的类声明：

class Player : public ScreenObject {
private:
    std::list<Thing*> inventory;

构造函数中没有对该列表进行任何操作。

Nothing is done to that list in the constructor.

失败的地方：

main.cpp：

Player pc(iname, w_choice, c_choice, 11, 11, WHITE, '@');

....

if (pc.addToInv(t)) {
    currentLevel.delObject(id);
}

....

player.cpp：

player.cpp:

int Player::addToInv(Thing& t) {
    if (inventory.size() <= 52) {
        inventory.push_back(&t);
    } else {
        shiplog("Cannot add to inventory, 52 item limit reached",10);
        return 0;
    }
}

使用gdb运行时出现的错误发生在调用size（），并到此结束：

The error I get when running it with gdb occurs on the call to size(), and ends up here:

Program received signal SIGSEGV, Segmentation fault.
0x0804eda6 in std::_List_const_iterator<Thing*>::operator++ (this=0xbfff9500)
at /usr/include/c++/4.4/bits/stl_list.h:223
223            _M_node = _M_node->_M_next;

任何猜测都非常感激！

完整的追踪是：

(gdb) bt
 0  0x0804e28a in std::_List_const_iterator<Thing*>::operator++ (
    this=0xbfff9500) at /usr/include/c++/4.4/bits/stl_list.h:223
 1  0x0804e64e in std::__distance<std::_List_const_iterator<Thing*> > (
    __first=..., __last=...)
    at /usr/include/c++/4.4/bits/stl_iterator_base_funcs.h:79
 2  0x0804e4d3 in std::distance<std::_List_const_iterator<Thing*> > (
    __first=..., __last=...)
    at /usr/include/c++/4.4/bits/stl_iterator_base_funcs.h:114
 3  0x0804e2e6 in std::list<Thing*, std::allocator<Thing*> >::size (
    this=0xbffff244) at /usr/include/c++/4.4/bits/stl_list.h:805
 4  0x0804df78 in Player::addToInv (this=0xbffff068, t=...) at player.cpp:551
 5  0x0804a873 in main (argc=1, argv=0xbffff494) at main.cpp:182

推荐答案

int Player::addToInv(Thing& t) {
if (inventory.size() <= 52) {
    inventory.push_back(&t);
} else {
    shiplog("Cannot add to inventory, 52 item limit reached",10);
    return 0;
}

}

通过引用传递，但其地址传递给inventory.push_back（）。尝试只传递't'。

Thing is passed by reference, but then its address is passed to inventory.push_back(). Try just passing 't'.

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