删除导致访问冲突的std :: list

时间：2013-05-28 09:49:38

标签： c++

对于学校项目，我的小组正在使用OpenCV来捕获视频。从这些（自上而下）图像中，提取对象的位置并将其转换为点列表。然后使用http://code.google.com/p/poly2tri/对这些点进行三角测量（以克服可能的非凸对象的问题）。然后，使用三角形地面窗格的坐标，我们使用freeglut以3D形式绘制对象。 （侧窗格和顶窗格使用地面窗格坐标计算）。我们遇到的问题是，当我们删除旧的Points列表时，应用程序会随机崩溃。有时1秒后，有时30秒后，有时几分钟后。我们得到的错误是“访问冲突写入位置0xCCCCCCCC”

我们的代码：

void WorldLayoutBuilder::update()
{
pointList.clear();

// Capture image
<code to capture image and get countours>

for(size_t i = 0; i < contours.size(); i++)
{
    if(contours[i].size() > 50)
    {
        approxPolyDP(contours[i], approxShape, cv::arcLength(cv::Mat(contours[i]), true)*0.04, true);
        drawContours(drawing, contours, i, cv::Scalar(255, 0, 0), 0);

        std::vector<Point> newObject;

        for(size_t j = 0; j < contours[i].size(); j++)
        {
            cv::Point newPoint = contours[i][j];    
            newObject.push_back(Point((float) newPoint.x / 100, 0.0f,(float) newPoint.y / 100));
        }

        pointList.push_back(newObject);
    }
}

ObjectCreator3D::createObjects(&pointList);
contours.clear();

<code to release images, etc>
}

这会捕获一个图像，检索对象的坐标，然后调用ObjectCreator3D :: createObjects（）：

void ObjectCreator3D::createObjects(std::list<std::vector<Point>>* inputList)
{
std::list<WorldObject>* tempObjects = new std::list<WorldObject>;

for(std::vector<Point>&pointObject : *inputList)
{                       
    WorldObject worldObject(&pointObject);
    tempObjects->push_back(worldObject);
}

DataStorage::getInstance()->setObjects(tempObjects);
}

所有对象都转换为WorldObjects：

#include <list>
#include <iostream>
#include <GL/glut.h>
#include <GL/freeglut.h>
#include <time.h>

#include "WorldObject.h"
#include "Point.h"

//Constant height - adjustable/randomized solution is partially implemented in the     constructor.
const float WorldObject::HEIGHT = 5.0f;

template <class C> void FreeClear(C & cntr)
{
for(typename C::iterator it = cntr.begin(); it != cntr.end(); ++it)
{
    delete * it;
}
cntr.clear();
}

WorldObject::WorldObject(std::vector<Point>* pointList)
{
//TODO, when we have time. Seems difficult because height will change each update...
/*srand (time(NULL));
float fGeneratedY = (rand() % 20 + 2) / 2.0f;*/

cdt = nullptr;

for (Point &point : *pointList) 
    //point.setY(fGeneratedY);
    point.setY(HEIGHT);

this->pointList = pointList;
}

WorldObject::~WorldObject()
{
//Cleanup
delete cdt;
FreeClear(polyPoints);
}

/*
Author Tim Cocu & Bas Rops
Function for drawing the WorldObject
*/
void WorldObject::draw()
{
glPushMatrix();

glColor3f(0.8f, 0.8f, 0.8f);

//Calculate our bottom pane
calculateTriangles();

//BOTTOM PANE
for (unsigned int i = 0; i < calculatedTriangles.size(); i++)
{
    p2t::Triangle& t = *calculatedTriangles[i];
    p2t::Point& a = *t.GetPoint(0);
    p2t::Point& b = *t.GetPoint(1);
    p2t::Point& c = *t.GetPoint(2);

    glBegin(GL_TRIANGLES);
        glNormal3f(0, -1, 0);
        glVertex3f((GLfloat)a.x, (GLfloat)0.0f, (GLfloat)a.y);
        glVertex3f((GLfloat)b.x, (GLfloat)0.0f, (GLfloat)b.y);
        glVertex3f((GLfloat)c.x, (GLfloat)0.0f, (GLfloat)c.y);
    glEnd();
}

//TOP PANE
for (unsigned int i = 0; i < calculatedTriangles.size(); i++)
{
    p2t::Triangle& t = *calculatedTriangles[i];
    p2t::Point& a = *t.GetPoint(0);
    p2t::Point& b = *t.GetPoint(1);
    p2t::Point& c = *t.GetPoint(2);

    glBegin(GL_TRIANGLES);
        glNormal3f(0, 1, 0);
        glVertex3f((GLfloat)a.x, (GLfloat)HEIGHT, (GLfloat)a.y);
        glVertex3f((GLfloat)b.x, (GLfloat)HEIGHT, (GLfloat)b.y);
        glVertex3f((GLfloat)c.x, (GLfloat)HEIGHT, (GLfloat)c.y);
    glEnd();
}

glColor3f(1.0f, 1.0f, 1.0f);

//SIDE PANES
for(std::size_t iPaneCounter = 0; iPaneCounter < pointList->size(); iPaneCounter++)
{
    Point firstPoint = (*pointList)[iPaneCounter];
    Point secondPoint (0.0f, 0.0f, 0.0f);

    if(iPaneCounter + 1 < pointList->size())
        secondPoint.set((*pointList)[iPaneCounter + 1].getX(), (*pointList)[iPaneCounter + 1].getY(), (*pointList)[iPaneCounter + 1].getZ() );
    else
        secondPoint.set((*pointList)[0].getX(), (*pointList)[0].getY(), (*pointList)[0].getZ());

    glBegin(GL_POLYGON);
        float fNormalX = (firstPoint.getY() * secondPoint.getZ()) - (firstPoint.getZ() * secondPoint.getY());
        float fNormalY = -((secondPoint.getZ() * firstPoint.getX()) - (secondPoint.getX() * firstPoint.getZ()));
        float fNormalZ = (firstPoint.getX() * secondPoint.getY()) - (firstPoint.getY() * secondPoint.getX());
        glNormal3f(fNormalX, fNormalY, fNormalZ);

        glVertex3f(firstPoint.getX(), 0.0f, firstPoint.getZ());
        glVertex3f(secondPoint.getX(), 0.0f, secondPoint.getZ());
        glVertex3f(secondPoint.getX(), secondPoint.getY(), secondPoint.getZ());
        glVertex3f(firstPoint.getX(), firstPoint.getY(), firstPoint.getZ());
    glEnd();
}
}

/*
Calculates triangles that make a ground or top pane. Used for calculating possible     non-convex objects
*/
void WorldObject::calculateTriangles()
{
//Empty the polyPoints list
if(polyPoints.size() > 0)
    FreeClear(polyPoints);

//Convert our Points to p2t::Points
for(std::size_t iBottomIndex = 0; iBottomIndex < pointList->size(); iBottomIndex++)
    polyPoints.push_back(new p2t::Point((*pointList)[iBottomIndex].getX(), (*pointList)[iBottomIndex].getZ()));

if(cdt == nullptr)
    //Create CDT (Constrained Delaunay Triangulation) and add primary polyPoints
    //NOTE: polyPoints must be a simple polygon. The polyPoints' points constitute constrained edges. No repeating points are allowed!
    cdt = new p2t::CDT(polyPoints);

//Turn our polyPoints into p2t::Triangles
cdt->Triangulate();

//Set the triangles to use for drawing
calculatedTriangles = cdt->GetTriangles();
}

/*
Retrieve a pointer to a list of Points
*/
std::vector<Point>* WorldObject::getPoints()
{
return pointList;
}

/*
Retrieve a pointer to a list of p2t::Triangles
*/
std::vector<p2t::Triangle*> WorldObject::getCalculatedTriangles()
{
return calculatedTriangles;
}

创建所有WorldObject后，它们存储在DataStorage中，调用DataStorage :: getInstance（） - ＆gt; setObjects（）：

void DataStorage::setObjects(std::list<WorldObject>* objectList)
{
delete this->objectList;
this->objectList = objectList;
}

应用程序似乎崩溃了删除this-＆gt; objectList;在setObjects（）中，我们认为应用程序试图删除他无法删除的内容。

任何帮助都将非常感谢，我们已经在这几天了

1 个答案:

答案 0 :(得分：3)

在这里，您将指向列表所拥有的对象的指针传递给WorldObject的构造函数：

for(std::vector<Point>&pointObject : *inputList)
{                       
  WorldObject worldObject(&pointObject);
  tempObjects->push_back(worldObject);
}

在WorldObject中存储指针：

//Default Constructor
WorldObject::WorldObject(std::vector<Point>* pointList)
{
  float fGeneratedY = (rand() % 20 + 2) / 2.0f;*/

  cdt = nullptr;

  for (Point &point : *pointList) 
    point.setY(HEIGHT);

  this->pointList = pointList;
}

这意味着WorldObject::pointList仅在您构建std::list s的WorldObject仍然存在的情况下才有效。 （在此之后，结果是未定义的 - 它可能会起作用，它可能会崩溃，它可能会格式化您的硬盘并将您的身份泄露给德克萨斯州。）

如果你坚持使用原始指针，你作为程序员负责检查和跟踪每个指针的生命周期。这很容易出错，并且会导致难以追踪的随机崩溃。

停止使用原始指针。相反，如果对象拥有资源，则将其存储在std::unique_ptr<>中。如果您希望多个对象共享相同的资源，请使用std::shared_ptr和std::weak_ptr，除非这些对象中的所有对象的生命周期都比其他对象的生命周期短得多。< / p>

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