链接问题C ++，问题和SDL

Question

我遇到了一些链接器错误，但我无法真正理解它们的含义，因此，我感谢您的帮助。 我正在尝试编写一个简单的程序，该程序仅创建一个基本的片段着色器和一个基本的顶点着色器。 这是代码：

Shader.h〜

#pragma once
#include <iostream>
#include <fstream>
#include <string>
#include <glew.h>


class Shader
{
    public:
    const static unsigned int NUMOFSHADERS = 2;

    GLuint m_program;
    GLuint m_shaders[NUMOFSHADERS];

    void Bind();
    static std::string LoadShader(const std::string& filename);
    static GLuint CreateShader(const std::string& text, GLenum shadertype);
    Shader(const std::string& filename);
    virtual ~Shader();
};

Shader.cpp〜

#include "Shader.h"


Shader::Shader(const std::string& filename)
{
    m_program = glCreateProgram();
    m_shaders[0] = CreateShader(LoadShader(filename + ".shade_v"),     GL_VERTEX_SHADER);
    m_shaders[1] = CreateShader(LoadShader(filename + ".shade_f"),     GL_FRAGMENT_SHADER);

    for (unsigned int i = 0; NUMOFSHADERS; i++)
    {
        glAttachShader(m_program, m_shaders[i]);
    };

    glBindAttribLocation(m_program, 0, "position");
    glLinkProgram(m_program);
}

Shader::~Shader()
{
    for (unsigned int i = 0; NUMOFSHADERS; i++)
    {
        glDetachShader(m_program, m_shaders[i]);
        glDeleteShader(m_shaders[i]);
    }

    glDeleteProgram(m_program);
}

static std::string LoadShader(const std::string& filename)
{

    std::ifstream file;
    std::string output;
    std::string line;
    file.open(filename.c_str());
    if (file.is_open())
    {
        while (file)
        {
            std::getline(file, line);
            output.append(line + "\n");
        }
        file.close();
        return output;
    }
}

static GLuint CreateShader(const std::string& text, GLenum shadertype)
{
    GLuint shader = glCreateShader(shadertype);
    const GLchar* shadersourcestrings[1];
    GLint shadersourcelengths[1];

    shadersourcestrings[0] = text.c_str();
    shadersourcelengths[0] = text.length();

    glShaderSource(shader, 1, shadersourcestrings, shadersourcelengths);
    glCompileShader(shader);

    return shader;
}

void Shader::Bind()
{
    glUseProgram(m_program);
}

Display.h〜

#pragma once
#include <SDL.h>
#include <glew.h>
#include <iostream>

class Display
{
public:
    void Update();
    void Clear(float r, float g, float b, float a);
    bool isClosed();
    Display(int width, int height, const char *title);
    virtual  ~Display();
private:
    bool m_isClosed;
    SDL_Window* m_window;
    SDL_GLContext m_context;
};

Display.cpp〜

#pragma once
#include "Display.h"

Display::Display(int width, int height, const char *title)
{
    if (SDL_Init(SDL_INIT_EVERYTHING) == 0)
    {
        SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);

        m_window = SDL_CreateWindow(title, SDL_WINDOWPOS_CENTERED,     SDL_WINDOWPOS_CENTERED, width, height, SDL_WINDOW_OPENGL);
        m_context = SDL_GL_CreateContext(m_window);

        GLenum status = glewInit();
        if (status != GLEW_OK){
            std::cerr << "this is where the problem is" << std::endl;
        }
        m_isClosed = false;
    }
}


Display::~Display()
{
        std::cerr << "destructor ran" << std::endl;
        SDL_GL_DeleteContext(m_context);
        SDL_DestroyWindow(m_window);
        SDL_Quit();
}

void Display::Update()
{
    SDL_Event event;
    SDL_GL_SwapWindow(m_window);

    while (SDL_PollEvent(&event))
    {
        switch (event.type)
        {
        case SDL_QUIT:
            m_isClosed = true;
        }
    }
}

void Display::Clear(float r, float g, float b, float a)
{
    glClearColor(r, g, b, a);
    glClear(GL_COLOR_BUFFER_BIT);
}

bool Display::isClosed(){
    return m_isClosed;
}

main.cpp〜

#include <iostream>
#include "Display.h"
#include "Shader.h"

int main(int argc, char *argv[])
{
    Display display(800, 600, "test");
    Shader shader("basicshader");

    while (!display.isClosed())
    {
        display.Clear(1.0f, 0.0f, 0.0f, 1.0f);
        shader.Bind();
        display.Update();
    }

    return 0;
}

这是我收到的错误 ：

error LNK2019: unresolved external symbol "public: static unsigned int __cdecl Shader::CreateShader(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &,unsigned int)" (?CreateShader@Shader@@SAIABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@I@Z) referenced in function "public: __thiscall Shader::Shader(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &)" (??0Shader@@QAE@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z)   C:\Users\Nas\documents\visual studio 2013\Projects\Open GL\Open GL\Shader.obj

error LNK2019: unresolved external symbol "public: static class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __cdecl Shader::LoadShader(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &)" (?LoadShader@Shader@@SA?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@ABV23@@Z) referenced in function "public: __thiscall Shader::Shader(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &)" (??0Shader@@QAE@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z) C:\Users\Nas\documents\visual studio 2013\Projects\Open GL\Open GL\Shader.obj

error LNK1120: 2 unresolved externals   C:\Users\Nas\documents\visual studio 2013\Projects\Open GL\Debug\Open GL.exe    1

Answer 1

您在CreateShader实现的CreateShader缺少Shader:: 。 另外，您必须在实现中删除static关键字：

         \/
GLuint Shader::CreateShader(const std::string& text, GLenum shadertype)
{
    ...
}

现在定义的是全局范围内的局部静态方法::CreateShader ，它与成员函数Shader::CreateShader完全无关。