我目前正在尝试使用OpenGl和C++编写基本的图形引擎。这样做时，OpenGl表现得很奇怪，没有明显的解释。它声称着色器无法编译，但是随后拒绝给出任何解释原因的错误。具体来说，当我调用glGetProgramiv时，返回值为0，但是glGetProgramInfoLog给出了一个空字符串¹。
这是一个最小的完整可验证示例:
#include <SDL2/SDL.h>
#include <GL/glew.h>
#include <sstream>
#include <stdexcept>
#include <fstream>
GLuint loadShader(const std::string &path, GLenum type);
int main(int argc, char *argv[]){
//show window & other housekeeping
SDL_Init(SDL_INIT_EVERYTHING);
SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 8);
SDL_GL_SetAttribute(SDL_GL_BUFFER_SIZE, 32);
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
SDL_Window *window = SDL_CreateWindow("test window", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 800, 600, SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE);
SDL_GLContext glContext = SDL_GL_CreateContext(window);
SDL_GL_MakeCurrent(window, glContext);
GLenum c = glewInit();
if(c != GLEW_OK){
std::ostringstream sout;
sout << "Failed to initialize OpenGl: " << glewGetErrorString(c);
throw std::runtime_error(sout.str());
}
//**** -- BEGIN IMPORTANT BIT -- ****//
//This is where the shaders are loaded
//load shaders
GLuint vertexShader = loadShader("shader.vert", GL_VERTEX_SHADER);
GLuint fragmentShader = loadShader("shader.frag", GL_FRAGMENT_SHADER);
//create & link program
GLuint program = glCreateProgram();
glAttachShader(program, vertexShader);
glAttachShader(program, fragmentShader);
glLinkProgram(program);
//check for errors
GLint success;
glGetProgramiv(program, GL_LINK_STATUS, &success);
if(!success){
GLchar infoLog[512];
GLint size; //gives 0 when checked in debugger
glGetProgramInfoLog(program, 512, &size, infoLog);
throw std::runtime_error(std::string("Failed to link shader program: ") + infoLog);
}
//cleanup
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
//**** -- END IMPORTANT BIT -- ****//
//update loop
bool isClosed = false;
while(!isClosed){
SDL_GL_SwapWindow(window);
SDL_Event e;
while(SDL_PollEvent(&e)){
switch(e.type){
case SDL_QUIT:
isClosed = true;
break;
}
}
}
}
GLuint loadShader(const std::string &path, GLenum type){
//load file
std::ifstream fin(path);
std::string line, total = "";
while(std::getline(fin, line)){
total += (line + "\n");
}
//reformat source into OpenGl's ridiculous format
const char *cArray = total.c_str();
const char **pointerToCArray = &cArray;
//create shader
GLuint shader = glCreateShader(type);
glShaderSource(shader, 1, pointerToCArray, nullptr);
glCompileShader(shader);
//check for erros
GLint success;
glGetShaderiv(shader, GL_COMPILE_STATUS, &success);
if(!success){
GLchar infoLog[512];
glGetShaderInfoLog(shader, 512, nullptr, infoLog);
throw std::runtime_error(std::string("Failed to compile shader: ") + infoLog);
}
}
MCVE testshader.vert:
#version 330 core
layout (location = 0) in vec3 position;
void main()
{
gl_Position = vec4(position.x, position.y, position.z, 1.0);
}
MCVE testshader.frag:
#version 330 core
out vec4 color;
void main()
{
color = vec4(1.0f, 0.5f, 0.2f, 1.0f);
}
运行此命令时，除了短暂闪烁窗口外，我还得到以下输出:
terminate called after throwing an instance of 'std::runtime_error'
what(): Failed to link shader program:
Aborted (core dumped)
附加说明:
libsdl2-dev和libglew-dev软件包安装的版本。我正在使用pkg-config进行链接。 在研究解决此错误的过程中，我主要发现了各种论坛和StackOverflow帖子，这些帖子在其他人的代码中发现了特定的错误。这些都不适用于我的代码，发现此错误后，我将我的代码与this假定有效的示例进行了比较。此示例还可以在我的计算机上编译并正确运行，从而排除了任何类型的配置错误。
¹:
glGetProgramInfoLog不可能对外部结果无所作为，并且infoLog数组恰巧在其第一个地址处分配了一个空终止符，因为即使glGetProgramInfoLog之前的大小返回值，即使glGetProgramInfoLog的大小返回也返回0叫做。 最佳答案
我发现了问题:loadShader()方法中缺少返回语句。但是，正如我在尝试解决此问题时所遇到的那样，这没有帮助。因此，我建议所有 future 阅读此书的人都找到一个工作示例(即this)，该示例与您尝试执行的操作类似，并将其代码的较小部分逐渐复制/粘贴到您的代码中(或Visa-反之亦然)执行一种二进制搜索来查找您的错误。