包含 header 时的 C++ OpenGL LNK2001

Question

我快28了

error LNK2001: unresolved external symbol

消息。我知道一个事实，例如，

glBindVertexArray

在 _int_gl_exts.h 中，果然我包含了它。

#include <glload\_int_gl_exts.h>

我不知道这是不是问题，但是我的错误信息中有三个下划线字符

symbol ___gleBindVertexArray

而在文件中，它前面只有两个下划线。这是包含文件中的确切行

extern PFNGLBINDVERTEXARRAYPROC __gleBindVertexArray;
#define glBindVertexArray __gleBindVertexArray

我的大部分内容都是直接从教程中提取的，即使我的包含和函数相同，我仍然遇到问题。如有必要，我会发布完整的代码，但在此处停留了大约 2 天后，我已经失去了想法。

编辑:我确实两者都有

#pragma comment(lib, "opengl32.lib")

我还尝试更改链接器中的项目属性以将其添加到其他库中。

我的整个代码如下。我知道还有很多其他的东西需要改变，但这是我首先要克服的。

#include <algorithm>
#include <string>
#include <vector>
#include <fstream>
#include <sstream>
#include <exception>
#include <stdexcept>
#include <string.h>
#include <glload/gl_3_3.h>
#include <glload/gll.hpp>
#include <glutil/Shader.h>
#include <GL/freeglut.h>
#include "framework.h"
#include "directories.h"
#include <glload/_int_gl_exts.h>

#ifdef LOAD_X11
#define APIENTRY
#endif

namespace Framework
{
GLuint LoadShader(GLenum eShaderType, const std::string &strShaderFilename)
{
    std::string strFilename = FindFileOrThrow(strShaderFilename);
    std::ifstream shaderFile(strFilename.c_str());
    std::stringstream shaderData;
    shaderData << shaderFile.rdbuf();
    shaderFile.close();

    try
    {
        return glutil::CompileShader(eShaderType, shaderData.str());
    }
    catch(std::exception &e)
    {
        fprintf(stderr, "%s\n", e.what());
        throw;
    }
}

GLuint CreateProgram(const std::vector<GLuint> &shaderList)
{
    try
    {
        GLuint prog = glutil::LinkProgram(shaderList);
        std::for_each(shaderList.begin(), shaderList.end(), glDeleteShader);
        return prog;
    }
    catch(std::exception &e)
    {
        std::for_each(shaderList.begin(), shaderList.end(), glDeleteShader);
        fprintf(stderr, "%s\n", e.what());
        throw;
    }
}

float DegToRad(float fAngDeg)
{
    const float fDegToRad = 3.14159f * 2.0f / 360.0f;
    return fAngDeg * fDegToRad;
}

std::string FindFileOrThrow( const std::string &strBasename )
{
    std::string strFilename = LOCAL_FILE_DIR + strBasename;
    std::ifstream testFile(strFilename.c_str());
    if(testFile.is_open())
        return strFilename;


    strFilename = GLOBAL_FILE_DIR + strBasename;
    testFile.open(strFilename.c_str());
    if(testFile.is_open())
        return strFilename;

    throw std::runtime_error("Could not find the file " + strBasename);
}
}


void init();
void display();
void reshape(int w, int h);
void keyboard(unsigned char key, int x, int y);

unsigned int defaults(unsigned int displayMode, int &width, int &height);

void APIENTRY DebugFunc(GLenum source, GLenum type, GLuint id, GLenum severity, GLsizei length,
           const GLchar* message, GLvoid* userParam)
{
std::string srcName;
switch(source)
{
case GL_DEBUG_SOURCE_API_ARB: srcName = "API"; break;
case GL_DEBUG_SOURCE_WINDOW_SYSTEM_ARB: srcName = "Window System"; break;
case GL_DEBUG_SOURCE_SHADER_COMPILER_ARB: srcName = "Shader Compiler"; break;
case GL_DEBUG_SOURCE_THIRD_PARTY_ARB: srcName = "Third Party"; break;
case GL_DEBUG_SOURCE_APPLICATION_ARB: srcName = "Application"; break;
case GL_DEBUG_SOURCE_OTHER_ARB: srcName = "Other"; break;
}

std::string errorType;
switch(type)
{
case GL_DEBUG_TYPE_ERROR_ARB: errorType = "Error"; break;
case GL_DEBUG_TYPE_DEPRECATED_BEHAVIOR_ARB: errorType = "Deprecated Functionality"; break;
case GL_DEBUG_TYPE_UNDEFINED_BEHAVIOR_ARB: errorType = "Undefined Behavior"; break;
case GL_DEBUG_TYPE_PORTABILITY_ARB: errorType = "Portability"; break;
case GL_DEBUG_TYPE_PERFORMANCE_ARB: errorType = "Performance"; break;
case GL_DEBUG_TYPE_OTHER_ARB: errorType = "Other"; break;
}

std::string typeSeverity;
switch(severity)
{
case GL_DEBUG_SEVERITY_HIGH_ARB: typeSeverity = "High"; break;
case GL_DEBUG_SEVERITY_MEDIUM_ARB: typeSeverity = "Medium"; break;
case GL_DEBUG_SEVERITY_LOW_ARB: typeSeverity = "Low"; break;
}

printf("%s from %s,\t%s priority\nMessage: %s\n",
    errorType.c_str(), srcName.c_str(), typeSeverity.c_str(), message);
}

int main(int argc, char** argv)
{
glutInit(&argc, argv);

int width = 500;
int height = 500;
unsigned int displayMode = GLUT_DOUBLE | GLUT_ALPHA | GLUT_DEPTH | GLUT_STENCIL;
displayMode = defaults(displayMode, width, height);

glutInitDisplayMode (displayMode);
glutInitContextVersion (3, 3);
glutInitContextProfile(GLUT_CORE_PROFILE);
#ifdef DEBUG
glutInitContextFlags(GLUT_DEBUG);
#endif
glutInitWindowSize (width, height); 
glutInitWindowPosition (300, 200);
int window = glutCreateWindow (argv[0]);

glload::LoadFunctions();

glutSetOption(GLUT_ACTION_ON_WINDOW_CLOSE, GLUT_ACTION_CONTINUE_EXECUTION);

if(!glload::IsVersionGEQ(3, 3))
{
    printf("Your OpenGL version is %i, %i. You must have at least OpenGL 3.3 to run this tutorial.\n",
        glload::GetMajorVersion(), glload::GetMinorVersion());
    glutDestroyWindow(window);
    return 0;
}

if(glext_ARB_debug_output)
{
    glEnable(GL_DEBUG_OUTPUT_SYNCHRONOUS_ARB);
    glDebugMessageCallbackARB(DebugFunc, (void*)15);
}

init();

glutDisplayFunc(display); 
glutReshapeFunc(reshape);
glutKeyboardFunc(keyboard);
glutMainLoop();
return 0;
}

#pragma comment(lib, "opengl32.lib")

#include <string>
#include <vector>
#include <math.h>
#include <stdio.h>
#include <string.h>
#include <glload/gl_3_3.h>
#include <glload\_int_gl_exts.h>
#include <GL/freeglut.h>
#include <glload\_int_gl_1_5.h>
#include <glload\_int_gl_1_1_rem_3_1.h>
#include "../../framework/framework.h"

#define GL_GLEXT_PROTOTYPES
#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif

GLuint theProgram;
GLuint elapsedTimeUniform;

void InitializeProgram()
{
std::vector<GLuint> shaderList;

shaderList.push_back(Framework::LoadShader(GL_VERTEX_SHADER, "calcOffset.vert"));
shaderList.push_back(Framework::LoadShader(GL_FRAGMENT_SHADER, "calcColor.frag"));

theProgram = Framework::CreateProgram(shaderList);

elapsedTimeUniform = glGetUniformLocation(theProgram, "time");

GLuint loopDurationUnf = glGetUniformLocation(theProgram, "loopDuration");
GLuint fragLoopDurUnf = glGetUniformLocation(theProgram, "fragLoopDuration");


glUseProgram(theProgram);
glUniform1f(loopDurationUnf, 5.0f);
glUniform1f(fragLoopDurUnf, 10.0f);
glUseProgram(0);
}

const float vertexPositions[] = {
0.25f, 0.25f, 0.0f, 1.0f,
0.25f, -0.25f, 0.0f, 1.0f,
-0.25f, -0.25f, 0.0f, 1.0f,
};

GLuint positionBufferObject;
GLuint vao;

void createCube() {
  glBegin(GL_LINES);
  glLineWidth(99.0);

  glColor3f(   1.0,  0.0, 1.0 );

  glVertex3f(  0.5,0.5,0.5 );
  glVertex3f(  0.5,0.5,-0.5 );

  glVertex3f( 0.5,0.5,-0.5 );
  glVertex3f( -0.5,0.5,-0.5 );

  glVertex3f( -0.5,0.5,-0.5 );
  glVertex3f( -0.5,0.5,0.5 );

  glVertex3f( -0.5,0.5,0.5 );
  glVertex3f( 0.5,0.5,0.5 );

  glVertex3f(  0.5,-0.5,0.5 );
  glVertex3f(  0.5,-0.5,-0.5 );

  glVertex3f( 0.5,-0.5,-0.5 );
  glVertex3f( -0.5,-0.5,-0.5 );

  glVertex3f( -0.5,-0.5,-0.5 );
  glVertex3f( -0.5,-0.5,0.5 );

  glVertex3f( -0.5,-0.5,0.5 );
  glVertex3f( 0.5,-0.5,0.5 );

  glVertex3f( 0.5,0.5,0.5 );
  glVertex3f( 0.5,-0.5,0.5 );

  glVertex3f( -0.5,-0.5,-0.5 );
  glVertex3f( -0.5,0.5,-0.5 );

  glVertex3f( 0.5,0.5,-0.5 );
  glVertex3f( 0.5,-0.5,-0.5 );

  glVertex3f( -0.5,0.5,0.5 );
  glVertex3f( -0.5,-0.5,0.5 );

  glEnd();
}

void InitializeVertexBuffer()
{
glGenBuffers(1, &positionBufferObject);

glBindBuffer(GL_ARRAY_BUFFER, positionBufferObject);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertexPositions), vertexPositions, GL_STREAM_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, 0);
}

//Called after the window and OpenGL are initialized. Called exactly once, before the main loop.
void init()
{
InitializeProgram();
InitializeVertexBuffer();

glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
}

//Called to update the display.
//You should call glutSwapBuffers after all of your rendering to display what you rendered.
//If you need continuous updates of the screen, call glutPostRedisplay() at the end of the function.
void display()
{
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glClear(GL_COLOR_BUFFER_BIT);

glUseProgram(theProgram);

glUniform1f(elapsedTimeUniform, glutGet(GLUT_ELAPSED_TIME) / 1000.0f);

glBindBuffer(GL_ARRAY_BUFFER, positionBufferObject);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0);


createCube();
glColor3f(1.0,0.0,0.0);
glutSolidSphere(0.04,10,10);

glDrawArrays(GL_TRIANGLES, 0, 3);

glDisableVertexAttribArray(0);
glUseProgram(0);

glutSwapBuffers();
glutPostRedisplay();
}

    //Called whenever the window is resized. The new window size is given, in pixels.
    //This is an opportunity to call glViewport or glScissor to keep up with the change in size.
void reshape (int w, int h)
{
glViewport(0, 0, (GLsizei) w, (GLsizei) h);
}

//Called whenever a key on the keyboard was pressed.
//The key is given by the ''key'' parameter, which is in ASCII.
//It's often a good idea to have the escape key (ASCII value 27) call glutLeaveMainLoop() to 
//exit the program.
void keyboard(unsigned char key, int x, int y)
{
switch (key)
{
case 27:
    glutLeaveMainLoop();
    return;
}
}


unsigned int defaults(unsigned int displayMode, int &width, int &height) {return displayMode;}

Answer 1

如果你真的说what library you were trying to link to就好了.我知道它是哪一个的唯一原因是因为我认得我自己的作品 ;)

无论如何，the documentation makes it clear what library you should link to .如果您使用的是 Premake4 构建系统，那么您的 premake4.lua 项目中应该只有 UseLibs {"glload"}。如果您正在使用其他东西，那么您需要分别在调试和发布中手动链接到 glloadD 或 glload。在 Windows 上，您需要一个 .lib 后缀；在 Linux 上，您将使用 libglloadD 等。

无论您是使用编译指示链接还是使用项目设置都无关紧要。