c++ - C++变量数据被覆盖

自编写C / C++以来已经有几年了，现在我面临着一个我似乎无法自行解决的问题。

给定以下结构:

struct InputData
{
    float diameter;
    float length;
    int vertIndex;
    struct InputData *parent;
    vector<InputData*> children;
    bool deadEnd;

    InputData(float dia, float lngth)
    {
        diameter = dia;
        length = lngth;
        vertIndex = NULL;
        parent = NULL;
        deadEnd = false;
    }
};

我首先定义了多个节点及其父/子关系:

InputData i0 = InputData(3.0f, 3.0f);
InputData i1 = InputData(2.0f, 2.0f);
InputData i2 = InputData(1.0f, 1.0f);
InputData i3 = InputData(1.0f, 1.0f);
InputData i4 = InputData(1.0f, 1.0f);
InputData i5 = InputData(1.01f, 0.5f);

i0.children.push_back(&i1);
i1.children.push_back(&i2);
i2.children.push_back(&i3);
i3.children.push_back(&i4);
i4.children.push_back(&i5);

i1.parent = &i0;
i2.parent = &i1;
i3.parent = &i2;
i4.parent = &i3;
i5.parent = &i4;

请注意，i5作为唯一节点没有任何子节点。

然后，我继续使用此数据做一些工作(从main()调用BuildMeshVertices(＆i0，＆vertices))，最后将一个子代添加到i5:

void BuildMeshVertices(InputData* current, vector<SimpleVertex> *vertices)
{
    //Do work

    if(current->children.size() == 1)
    {
        BuildMeshVertices(current->children[0], vertices);
    }
    else if(current->children.size() == 0 && current->deadEnd == false)
    {
        InputData iDeadEnd = InputData(1.01f, 0.5f);
        iDeadEnd.deadEnd = true;
        iDeadEnd.parent = current;
        current->children.push_back(&iDeadEnd);

        BuildMeshVertices(&iDeadEnd, vertices);
    }
}

之后一切都很好。 i0有一个 child (i1)，i1有一个 child (i2)，依此类推，i5现在也有一个 child 。

我调用了另一个函数(BuildMeshIndices())，突然在此函数中插入了几行(第63行)，新添加到i5的子级的数据被覆盖了。 i5仍然指向正确的 child ，但是该 child 的数据突然出现乱码。

这是before and after的屏幕截图(很抱歉，该链接，但不允许我使用IMG标签)

我不知道为什么会这样，但是我感觉到这与我糟糕的内存管理有关吗？

UPDATE 也不是必须这样做。例如，如果将子级 vector 更改为值 vector 是首选的C++方法，那么我将更愿意这样做。我已经尝试对答案发表评论，但是我不确定你们是否看到了评论(根据常见问题解答，您需要50点信誉才能发表评论)？

以下是完整的源代码(删除了所有不必要的内容，但足以重现该错误):

#include "stdafx.h"
#include <vector>

using std::vector;

struct InputData
{
    float diameter;
    float length;
    int vertIndex;
    struct InputData *parent;
    vector<InputData*> children;
    bool deadEnd;

    InputData(float dia, float lngth)
    {
        diameter = dia;
        length = lngth;
        vertIndex = NULL;
        parent = NULL;
        deadEnd = false;
    }
};

//--------------------------------------------------------------------------------------
// Vertex types
//--------------------------------------------------------------------------------------
struct SimpleVertex
{
    float Pos;

    SimpleVertex(float Position)
    {
        Pos = Position;
    }
};

void BuildMeshVertices(InputData* current, vector<SimpleVertex> *vertices)
{
    current->vertIndex = vertices->size();

    //Add vertices..

    if(current->children.size() == 1)
    {
        BuildMeshVertices(current->children[0], vertices);
    }
    else if(current->children.size() == 0 && current->deadEnd == false)
    {
        InputData iDeadEnd = InputData(1.01f, 0.5f);
        iDeadEnd.deadEnd = true;
        iDeadEnd.parent = current;
        current->children.push_back(&iDeadEnd);

        BuildMeshVertices(&iDeadEnd, vertices);
    }
}

void BuildMeshIndices(InputData* current, vector<unsigned long> *indices)
{
    indices->push_back(current->vertIndex+2);
    indices->push_back(current->vertIndex+0);
    indices->push_back(current->vertIndex+1);
    indices->push_back(current->vertIndex+3);
    indices->push_back(current->vertIndex+0);
    indices->push_back(current->vertIndex+2);

    InputData *parent = current->parent;

    unsigned long vOffset;

    if(parent != NULL && parent->children.size() == 1)
    {
        vOffset = (unsigned long)current->vertIndex;

        indices->push_back(vOffset+7);
        indices->push_back(vOffset+5);
        indices->push_back(vOffset+4);
        indices->push_back(vOffset+6);
        indices->push_back(vOffset+5);
        indices->push_back(vOffset+7);

        indices->push_back(vOffset+10);
        indices->push_back(vOffset+8);
        indices->push_back(vOffset+9);
        indices->push_back(vOffset+11);
        indices->push_back(vOffset+8);
        indices->push_back(vOffset+10);

        indices->push_back(vOffset+15);
        indices->push_back(vOffset+13);
        indices->push_back(vOffset+12);
        indices->push_back(vOffset+14);
        indices->push_back(vOffset+13);
        indices->push_back(vOffset+15);

        indices->push_back(vOffset+18);
        indices->push_back(vOffset+16);
        indices->push_back(vOffset+17);
        indices->push_back(vOffset+19);
        indices->push_back(vOffset+16);
        indices->push_back(vOffset+18);
    }

    if(current->children.size() == 1 && current->deadEnd == false)
    {
        BuildMeshIndices(current->children[0], indices);
    }
}

int _tmain(int argc, _TCHAR* argv[])
{
    InputData i0 = InputData(3.0f, 3.0f);
    InputData i1 = InputData(2.0f, 2.0f);
    InputData i2 = InputData(1.0f, 1.0f);
    InputData i3 = InputData(1.0f, 1.0f);
    InputData i4 = InputData(1.0f, 1.0f);
    InputData i5 = InputData(1.01f, 0.5f);

    i0.children.push_back(&i1);
    i1.children.push_back(&i2);
    i2.children.push_back(&i3);
    i3.children.push_back(&i4);
    i4.children.push_back(&i5);

    i1.parent = &i0;
    i2.parent = &i1;
    i3.parent = &i2;
    i4.parent = &i3;
    i5.parent = &i4;

    // Create vertex buffer
    vector<SimpleVertex> vertices;

    BuildMeshVertices(&i0, &vertices);

    // Create index buffer
    vector<unsigned long> indices;

    BuildMeshIndices(&i0, &indices);

    return 0;
}

最佳答案

将原始指针更改为smart pointers，您将遇到内存管理问题。

您不需要将所有boost都复制到您的项目中，只需复制所需的标题即可。

#include <vector>
#include <boost/shared_ptr.hpp>
#include <boost/weak_ptr.hpp>

struct InputData
{
    float diameter;
    float length;
    unsigned long vertIndex;
    boost::weak_ptr<InputData> parent;
    std::vector< boost::shared_ptr<InputData> > children;
    bool deadEnd;

    InputData(float dia, float lngth, boost::weak_ptr<InputData> p = boost::weak_ptr<InputData>(), bool de = false)
        : diameter(dia), length(lngth), vertIndex(0), parent(p), deadEnd(de) {}
};

struct SimpleVertex
{
    float Pos;

    SimpleVertex(float position) : Pos(position) {}
};

void BuildMeshVertices(boost::shared_ptr<InputData> current, std::vector<SimpleVertex>& vertices)
{
    current->vertIndex = vertices.size();

    //Add vertices..
    if(current->children.size() == 1)
    {
        BuildMeshVertices(current->children[0], vertices);
    }
    else if(current->children.size() == 0 && current->deadEnd == false)
    {
          // this was a stack variable, so the pointer became invalid when going out of ambit.
        boost::shared_ptr<InputData> iDeadEnd( new InputData(1.01f, 0.5f, current, true) );
        current->children.push_back(iDeadEnd);

        BuildMeshVertices(iDeadEnd, vertices);
    }
}

void BuildMeshIndices(boost::shared_ptr<InputData> current, std::vector<unsigned long>& indices)
{
    unsigned long vi = current->vertIndex;
    unsigned long  ioffset[] = { vi+2, vi, vi+1, vi+3, vi, vi+2};
    indices.insert(indices.end(), ioffset, ioffset+6);

    boost::shared_ptr<InputData> parent = current->parent.lock();
    if (parent && parent->children.size() == 1)
    {
        unsigned long offs = current->vertIndex;
          unsigned long voffset[] =
          { offs+7, offs+5, offs+4, offs+6, offs+5, offs+7,
            offs+10, offs+8, offs+9, offs+11, offs+8, offs+10,
            offs+15, offs+13, offs+12, offs+14, offs+13, offs+15,
            offs+18, offs+16, offs+17, offs+19, offs+16, offs+18 };
          indices.insert(indices.end(), voffset, voffset+24);
    }

    if(current->children.size() == 1 && current->deadEnd == false)
    {
        BuildMeshIndices(current->children[0], indices);
    }
}

int main()
{
    boost::shared_ptr<InputData> i0( new InputData(3.0f, 3.0f) );
    boost::shared_ptr<InputData> i1( new InputData(2.0f, 2.0f) );
    boost::shared_ptr<InputData> i2( new InputData(1.0f, 1.0f) );
    boost::shared_ptr<InputData> i3( new InputData(1.0f, 1.0f) );
    boost::shared_ptr<InputData> i4( new InputData(1.0f, 1.0f) );
    boost::shared_ptr<InputData> i5( new InputData(1.01f, 0.5f) );

    i0->children.push_back(i1);
    i1->children.push_back(i2);
    i2->children.push_back(i3);
    i3->children.push_back(i4);
    i4->children.push_back(i5);

    i1->parent = i0;
    i2->parent = i1;
    i3->parent = i2;
    i4->parent = i3;
    i5->parent = i4;

    // Create vertex buffer
    std::vector<SimpleVertex> vertices;
    BuildMeshVertices(i0, vertices);

    // Create index buffer
    std::vector<unsigned long> indices;
    BuildMeshIndices(i0, indices);

    return 0;
}

认为您仍然有一半的C，一半的C++脏代码...您应该选择一种语言。