調用OpenGL函數時程序崩潰

Question

我正在嘗試設置一個遊戲引擎項目。我的視覺工作室項目的設置是爲了讓我的'引擎'項目與我的'遊戲'項目分開。然後將引擎項目編譯爲一個dll供遊戲項目使用。我已經下載並設置了glfw和glew開始使用openGL。我的問題是，當我打我的第一個openGL函數時，程序崩潰。我知道這與glewinit有關，即使glew成功初始化（沒有控制檯錯誤）。在我的發動機項目，我有一個窗口類，其中，在窗口建設，GLEW應設置：

在window.h

#pragma once 
#include "GL\glew.h" 
#include "GLFW\glfw3.h" 

#if (_DEBUG) 
#define LOG(x) printf(x) 
#else 
#define LOG(x) 
#endif 

namespace BlazeGraphics 
{ 

    class __declspec(dllexport) Window 
    { 
    public: 
     Window(short width, short height, const char* title); 
     ~Window(); 

     void Update(); 
     void Clear() const; 
     bool Closed() const; 

    private: 
     int m_height; 
     int m_width; 
     const char* m_title; 
     GLFWwindow* m_window; 

    private: 
     Window(const Window& copy) {} 
     void operator=(const Window& copy) {} 
    }; 

} 

Window.cpp（其中glewinit（）被調用）

#include "Window.h" 
#include <cstdio> 

namespace BlazeGraphics 
{ 

    //Needed to define outside of the window class (not sure exactly why yet) 
    void WindowResize(GLFWwindow* window, int width, int height); 

    Window::Window(short width, short height, const char* title) : 
     m_width(width), 
     m_height(height), 
     m_title(title) 
    { 
     //InitializeWindow 
     { 
      if (!glfwInit()) 
      { 
       LOG("Failed to initialize glfw!"); 
       return; 
      }; 

      m_window = glfwCreateWindow(m_width, m_height, m_title, NULL, NULL); 
      if (!m_window) 
      { 
       LOG("Failed to initialize glfw window!"); 
       glfwTerminate(); 
       return; 
      }; 

      glfwMakeContextCurrent(m_window); 
      glfwSetWindowSizeCallback(m_window, WindowResize); 
     } 

     //IntializeGl 
     { 
      //This needs to be after two functions above (makecontextcurrent and setwindowresizecallback) or else glew will not initialize 
      **if (glewInit() != GLEW_OK) 
      { 
       LOG("Failed to initialize glew!"); 
      }** 
     } 
    } 


    Window::~Window() 
    { 
     glfwTerminate(); 
    } 

    void Window::Update() 
    { 
     glfwPollEvents(); 
     glfwSwapBuffers(m_window); 
    } 

    void Window::Clear() const 
    { 
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
    } 

    //Returns a bool because glfwwindowShouldClose returns a nonzero number or zero 
    bool Window::Closed() const 
    { 
     //Made it equal to 1 to take away warning involving converting an int to bool 
     return glfwWindowShouldClose(m_window) == 1; 
    } 

    //Not part of window class so defined above 
    void WindowResize(GLFWwindow* window, int width, int height) 
    { 
     glViewport(0, 0, width, height); 
    } 

} 

這是這是我的遊戲項目，我現在有我的OpenGL功能在全局函數（只是現在）內發現了我的main.cpp文件：

的main.cpp

#include <iostream> 
#include <array> 
#include <fstream> 
#include "GL\glew.h" 
#include "GLFW\glfw3.h" 
#include "../Engine/Source/Graphics/Window.h" 

void initializeGLBuffers() 
{ 
    GLfloat triangle[] = 
    { 
     +0.0f, +0.1f, -0.0f, 
     0.0f, 1.0f, 0.0f, 

     -0.1f, -0.1f, 0.0f, //1 
     0.0f, 1.0f, 0.0f, 

     +0.1f, -0.1f, 0.0f, //2 
     0.0f, 1.0f, 0.0f, 
    }; 

    GLuint bufferID; 
    glGenBuffers(1, &bufferID); 
    glBindBuffer(GL_ARRAY_BUFFER, bufferID); 
    glBufferData(GL_ARRAY_BUFFER, sizeof(triangle), triangle, GL_STATIC_DRAW); 
    glEnableVertexAttribArray(0); 
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, (sizeof(GLfloat)) * 6, nullptr); 
    glEnableVertexAttribArray(1); 
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, (sizeof(GLfloat)) * 6, (char*)((sizeof(GLfloat)) * 3)); 

    GLushort indices[] = 
    { 
     0,1,2 
    }; 

    GLuint indexBufferID; 
    glGenBuffers(1, &indexBufferID); 
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBufferID); 
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW); 
}; 


void installShaders() 
{ 
    //Create Shader 
    GLuint vertexShaderID = glCreateShader(GL_VERTEX_SHADER); 
    GLuint FragmentShaderID = glCreateShader(GL_FRAGMENT_SHADER); 

    //Add source or text file to shader object 
    std::string temp = readShaderCode("VertexShaderCode.glsl"); 
    const GLchar* adapter[1]; 

    adapter[0] = temp.c_str(); 
    glShaderSource(vertexShaderID, 1, adapter, 0); 
    temp = readShaderCode("FragmentShaderCode.glsl").c_str(); 
    adapter[0] = temp.c_str(); 
    glShaderSource(FragmentShaderID, 1, adapter, 0); 

    //Compile Shadaer 
    glCompileShader(vertexShaderID); 
    glCompileShader(FragmentShaderID); 

    if (!checkShaderStatus(vertexShaderID) || !checkShaderStatus(FragmentShaderID)) 
     return; 

    //Create Program 
    GLuint programID = glCreateProgram(); 
    glAttachShader(programID, vertexShaderID); 
    glAttachShader(programID, FragmentShaderID); 

    //Link Program 
    glLinkProgram(programID); 

    if (!checkProgramStatus(programID)) 
    { 
     std::cout << "Failed to link program"; 
     return; 
    } 

    //Use program 
    glUseProgram(programID); 
} 

int main() 
{ 

    BlazeGraphics::Window window(1280, 720, "MyGame"); 

    initializeGLBuffers(); 
    installShaders(); 

    while (!window.Closed()) 
    { 
     window.Clear(); 

     glDrawElements(GL_TRIANGLES, 3, GL_UNSIGNED_SHORT, 0); 

     window.Update(); 
    }; 

    return 0; 
} 

現在，如果我是在我的main.cpp這裏移動glewinit（）代碼：

int main() 
{ 

    BlazeGraphics::Window window(1280, 720, "MyGame"); 

    if (glewInit() != GLEW_OK) 
      { 
       LOG("Failed to initialize glew!"); 
      } 

    initializeGLBuffers(); 
    installShaders(); 

    while (!window.Closed()) 
    { 
     window.Clear(); 

     glDrawElements(GL_TRIANGLES, 3, GL_UNSIGNED_SHORT, 0); 

     window.Update(); 
    }; 

    return 0; 
} 

然後我的程序編譯罰款。爲什麼試圖在engine.dll中初始化glew導致程序崩潰？謝謝你的幫助。

Answer 1

GLEW通過爲每個OpenGL函數定義一個函數指針全局變量來工作。讓我們來看看glBindBuffer爲例：

#define GLEW_FUN_EXPORT GLEWAPI 

typedef void (GLAPIENTRY * PFNGLBINDBUFFERPROC) (GLenum target, GLuint buffer); 
GLEW_FUN_EXPORT PFNGLBINDBUFFERPROC __glewBindBuffer; 

所以我們只是有一個__glewBindBuffer函數指針，這將是glewInit被設置爲正確的地址，從你的OpenGL實現。

居然能寫出glBindBuffer，GLEW簡單地定義預處理器宏映射GL功能，這些函數指針變量：

#define glBindBuffer GLEW_GET_FUN(__glewBindBuffer); 

爲什麼試圖內engine.dll導致程序崩潰GLEW初始化？

因爲你的engine.dll和你的主應用程序每個都有一個單獨的所有這些全局變量的集合。您必須從您的引擎DLL中導出所有__glew*變量，以便能夠訪問您在engine.dll中呼叫的glewInit呼叫的結果。