Visual Studio const_iterator分配错误 [英] Visual Studio const_iterator Assignment Error

问题描述

在Visual Studio 2010上分配一个默认构造的向量< int *> :: const_iterator 错误。我在5个Visual Studio 2010系统上试过，有Service Pack 1.它在3/5机器上失败，我已经能够识别3个系统上导致故障的原因，但我似乎找不到错误报告。

The assignment of a default constructed vector<int*>::const_iterator errors on Visual Studio 2010. I've tried this on 5 Visual Studio 2010 systems that all have Service Pack 1. It fails on 3/5 machines, I've been able to identify what is causing the failure on the 3 systems but I cannot seem to find a bug report.

这里是代码：

#include <iostream>
#include <vector>

using namespace std;

int main() {
    vector<int*> vec;
    int arr[3] = {};

    for(int i = 0; i < sizeof(arr) / sizeof(arr[0]); ++i) vec.push_back(arr + i);

    vector<int*>::const_iterator initialized = vec.cbegin();
    vector<int*>::const_iterator uninitialized;

    initialized = uninitialized;

    cout << "Hello World" << endl;

    return 0;
}

显然，除了 cout< Hello World< endl; 在Release中进行了优化，因此这个最小示例只会在Debug中失败。但在Debug中，它给出的错误是：

Clearly everything but the cout << "Hello World" << endl; is optimized out in Release so this minimal example will only fail in Debug. But in Debug the error it gives is:

在test.exe中0x01071e14处的未处理异常：0xC0000005：访问冲突读取位置0x00000000。 p>

Unhandled exception at 0x01071e14 in test.exe: 0xC0000005: Access violation reading location 0x00000000.

比较链接的工作和非工作MSVCP100D.dll显示存在微小差异，工作.dll是产品版本： 10.0.40219.325和非工作的.dll是产品版本：10.0.40219.1。

Comparing the working and non-working MSVCP100D.dlls that were linked shows that there is a slight discrepancy, the working .dll is Product Version: 10.0.40219.325 and the non-working .dll is Product Version: 10.0.40219.1.

实际错误发生在

C：\Program Files（x86）\ Microsoft Visual Studio 10.0 \VC\include\xutility

C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\include\xutility

再次区分工作版本和非工作版本显示已对工作版本进行了更改。非工作代码简单地说：

And again diffing the working and non-working version shows that a change has been made to the working version. The non-working code simply says:

if (_Myproxu != _Right._Myproxy)
    _Adopt(_Right._Myproxy->_Mycont);

工作代码说：

if (_Myproxy == _Right._Myproxy)
    ;
else if (_Right._Myproxy != 0)
    _Adopt(_Right._Myproxy->_Mycont);
else
    {   // becoming invalid, disown current parent
    _Lockit _Lock(_LOCK_DEBUG);
    _Orphan_me();
    }

这就是我的实际问题。如何获取此更新？我已更新到最新使用Windows更新，但问题还没有解决。有没有一些隐藏的补丁，我需要去某个地方得到？我找不到这个问题写在任何地方，所以我也找不到有关补丁的信息。

All that to say, here's my actual question. How do I get this update? I've updated to the latest using Windows Update, but the problem has not been resolved. Is there some hidden patch that I need to go somewhere to get? I can't find this issue written up anywhere, so I also can't find information about the patch.

推荐答案

有未定义的行为。 [iterator.requirements.general] / p6：

This code has undefined behavior. [iterator.requirements.general]/p6:

迭代器也可以有与
任何序列无关的奇异值。 [示例：在声明未初始化的
指针 x 之后（如 int * x; ）， x 必须总是假定有一个指针的
奇异值。 - end example ]大多数
表达式的结果未定义为奇异值;唯一的例外是
破坏一个拥有奇异值的迭代器，将
a非奇异值赋值给一个拥有奇异值的迭代器，
用于满足 DefaultConstructible 需求，
使用值初始化的迭代器作为副本或移动
操作的源。 [注意：：此保证不提供默认
初始化，虽然区别只对具有
类型的类型有意义，例如指针或聚合保存
指针的默认构造函数。 - end note ]在这些情况下，奇异值是
覆盖的方式与任何其他值相同。可拒绝值
总是非奇异的。

Iterators can also have singular values that are not associated with any sequence. [ Example: After the declaration of an uninitialized pointer x (as with int* x;), x must always be assumed to have a singular value of a pointer. —end example ] Results of most expressions are undefined for singular values; the only exceptions are destroying an iterator that holds a singular value, the assignment of a non-singular value to an iterator that holds a singular value, and, for iterators that satisfy the DefaultConstructible requirements, using a value-initialized iterator as the source of a copy or move operation. [ Note: This guarantee is not offered for default initialization, although the distinction only matters for types with trivial default constructors such as pointers or aggregates holding pointers. —end note ] In these cases the singular value is overwritten the same way as any other value. Dereferenceable values are always non-singular.

未初始化

但是，考虑到你发布的代码段，我怀疑你的代码不会即使您的值初始化未初始化，这是Microsoft的实现中的错误，并且它们在后续修补程序。

However, given the snippets you post, I suspect that your code wouldn't work either even if you value-initialize uninitialized, which is a bug in Microsoft's implementation, and which they fixed in a later hotfix.

这篇关于Visual Studio const_iterator分配错误的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！