Question

我最近遇到过使用openGL的问题。在我之前运行良好的程序中，我尝试在屏幕上绘制一组多边形，但程序会抛出一个错误，而对于我的生活，我无法找到它的原因。我几乎从我的代码中没有改变，它只是在一个月后回到它之后的一天开始抛出错误。错误是：

Unhandled exception at 0x69F2883E (nvoglv32.dll) in openGLtest.exe: 
0xC0000005: Access violation reading location 0x00000000.

我已使用以下代码重现了错误。我注意到的一些更奇怪的行为是，如果我将对glDrawArrays的调用更改为：

glDrawArrays(GL_TRIANGLES, 3, numV);

或

glDrawArrays(GL_TRIANGLES, 0, 258);

然后程序不会抛出错误，但显然它没有正确渲染，只渲染矩形的一半，或渲染矩形加上一些垃圾输入。

这很奇怪，如果它渲染超过255点它可以正常工作但不会更少，它会引发错误。

#include <SDL.h>
#include <GL/glew.h>
#include <math.h>
#include <vector>

struct Vector2f{
public:
    float x, y;
    Vector2f() {}
    Vector2f(float _x, float _y) { x = _x; y = _y; }
};
struct Vector3f {
public:
    float x, y, z;
    Vector3f() { x = 0.0, y = 0.0, z = 0.0; }
    Vector3f(float _x, float _y, float _z) { x = _x; y = _y; z = _z; }
};
struct Vertex {
    Vector3f m_pos;
    Vector2f m_tex;
    Vector3f m_normal;
    Vertex() {}
    Vertex(Vector3f pos, Vector2f tex) {
        m_pos = pos;
        m_tex = tex;
        m_normal = Vector3f(0.0f, 0.0f, 0.0f);
    }
    Vertex(Vector3f pos, Vector2f tex, Vector3f norm) {
        m_pos = pos;
        m_tex = tex;
        m_normal = norm;
    }
};

SDL_Window*         Window_Display  = NULL;
SDL_GLContext       glcontext;
GLuint              VBO;
int                 width           = 800;
int                 height          = 600;
float               ratio           = (float)width / (float)height;
int                 numV;
std::vector<Vertex> _VBO;

bool initWindow() {
    //draw a square
    _VBO.push_back(Vertex(Vector3f(-0.8f, -0.8f, 0.0f), Vector2f(0.0f, 0.0f), Vector3f(0.0f, 0.0f, 0.0f)));
    _VBO.push_back(Vertex(Vector3f(0.8f, -0.8f, 0.0f),  Vector2f(0.0f, 0.0f), Vector3f(0.0f, 0.0f, 0.0f)));
    _VBO.push_back(Vertex(Vector3f(0.8f, 0.8f, 0.0f),   Vector2f(0.0f, 0.0f), Vector3f(0.0f, 0.0f, 0.0f)));
    _VBO.push_back(Vertex(Vector3f(-0.8f, -0.8f, 0.0f), Vector2f(0.0f, 0.0f), Vector3f(0.0f, 0.0f, 0.0f)));
    _VBO.push_back(Vertex(Vector3f(-0.8f, 0.8f, 0.0f),  Vector2f(0.0f, 0.0f), Vector3f(0.0f, 0.0f, 0.0f)));
    _VBO.push_back(Vertex(Vector3f(0.8f, 0.8f, 0.0f),   Vector2f(0.0f, 0.0f), Vector3f(0.0f, 0.0f, 0.0f)));
    numV = 6;

    if (SDL_Init(SDL_INIT_VIDEO) < 0) return false;
    if ((Window_Display = SDL_CreateWindow("OpenGL Drawing Test", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, width, height, SDL_WINDOW_OPENGL)) == NULL) return false;

    glcontext = SDL_GL_CreateContext(Window_Display);

    glewInit();

    return true;
}

bool drawScene() {
    glEnableClientState(GL_VERTEX_ARRAY);

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glMatrixMode(GL_MODELVIEW); //Switch to the drawing perspective
    glLoadIdentity(); //Reset the drawing perspective

    glEnableVertexAttribArray(0);
    glEnableVertexAttribArray(1);
    glEnableVertexAttribArray(2);

    glGenBuffers(1, &VBO);
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, numV * sizeof(Vertex), &_VBO[0], GL_STATIC_DRAW);

    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0);
    glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*)12);
    glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*)20);
    glDrawArrays(GL_TRIANGLES, 0, numV);    //Unhandled exception at 0x69F2883E (nvoglv32.dll) in openGLtest.exe: 0xC0000005: Access violation reading location 0x00000000.

    glDisableVertexAttribArray(0);
    glDisableVertexAttribArray(1);
    glDisableVertexAttribArray(2);

    SDL_GL_SwapWindow(Window_Display); //Send the 3D scene to the screen

    glDisableClientState(GL_VERTEX_ARRAY);

    return true;
}

int main(int argc, char* args[]) {
    if (initWindow()) {
        while (drawScene()) {}
    }
    return 0;
}

nvoglv32.dll访问冲突读取位置0x00000000

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