7 replies to this topic

[ShotoReaper]

Hi!
I have the next code, where I get an error and the program close:

main

[...]
glUseProgram(shader->ID);
ExitOnGLError("ERROR: Could use the shader");    
[...]

util.cpp

void ExitOnGLError(const char* error_message)
{
const GLenum ErrorValue = glGetError();
cout<<ErrorValue<<endl;     //output '1282'
if(ErrorValue != GL_NO_ERROR)
{
	 cout<<"hola "<<ErrorValue<<endl;
  const char* APPEND_DETAIL_STRING = ": %s\n";
  // strlen: retorna un numero de caracteres
  const size_t APPEND_LENGTH = strlen(APPEND_DETAIL_STRING) + 1;
  const size_t message_length = strlen(error_message);
  char* display_message = (char*)malloc(message_length + APPEND_LENGTH);
  memcpy(display_message, error_message, message_length);
  memcpy(&display_message[message_length], APPEND_DETAIL_STRING, APPEND_LENGTH);
  fprintf(stderr, display_message, gluErrorString(ErrorValue));
  free(display_message);
  exit(EXIT_FAILURE);
}
}

But if I use this code, I don´t get any error and the program works!

main

glUseProgram(shader->ID);
const GLenum ErrorValue = glGetError();
cout<<ErrorValue<<endl;     // output '0'
ExitOnGLError("ERROR: Could use the shader");     // Any error here and the program continue..

Does anyone know why this is happening?

[SuperVGA]

The reason the latter works is that glGetError() is called twice, and as the first one is called without resulting in an error, glGetError() returns 0 inside the ExitOnGLError() function.

IIRC, 1282 Means invalid value. - Are you sure that shader->ID was created from a glLinkProgram() successfully prior to that?

[ShotoReaper]

The reason the latter works is that glGetError() is called twice, and as the first one is called without resulting in an error, glGetError() returns 0 inside the ExitOnGLError() function.

IIRC, 1282 Means invalid value. - Are you sure that shader->ID was created from a glLinkProgram() successfully prior to that?

I think that the program was linked successfully.

void CheckLink(GLuint id)
{
    //CheckAndLog(id,GL_LINK_STATUS,"conexion");
    GLint compiled = 0;
    GLint length = 0;
    glGetProgramiv(id, GL_LINK_STATUS, &compiled);
    if(compiled == 0)
    {
	    std::cerr<<"ERROR: linking fail"<<std::endl;
	    glGetProgramiv(id, GL_INFO_LOG_LENGTH, &length);
	    if(length > 1) {
		 std::string log(length, '\0');
		 glGetProgramInfoLog(id, length, &length, &log[0]);
		 std::cerr<<log<<std::endl;
		 exit(1);
	    }
    }else
    {
	    std::cout<<"linkage was successfully"<<std::endl;
    }

This code don´t give me any error

[Brother Bob]

Show more code, preferably a minimum complete program. There is likely more to this problem that what you have shown. For example, if you're only checking the error state after glUseProgram, then the error could be at any point before that because error bits are never reset by functions other that glGetError so the error can come from earlier functions within your program.

[ShotoReaper]

engine.cpp

void Engine::CreateMesh(void)
{
	mesh = content.Load<Mesh>("Models/cube2.obj");
	
	shader = content.Load<Shader>("Shaders/simpleshader.glsl");
  
	ModelMatrixUniformLocation = shader->GetUniformLocation("ModelMatrix");
	ViewMatrixUniformLocation = shader->GetUniformLocation("ViewMatrix");
	ProjectionMatrixUniformLocation = shader->GetUniformLocation("ProjectionMatrix");
	ExitOnGLError("ERROR: Could not get the uniform locations");

	Texture* texture0 = content.Load<Texture>("Textures/cube.bmp");
	Tex0Loc = shader->GetUniformLocation("texture0");  
	ExitOnGLError("Error: Could not load texture");
}

void Engine::DrawMesh(void)
{

	glUseProgram(shader->ID);
	ExitOnGLError("ERROR: Could not use the shader");	 // Error 1282

	glUniformMatrix4fv(ModelMatrixUniformLocation, 1, GL_FALSE, value_ptr(ModelMatrix));
	ExitOnGLError("ERROR: Could not set the model matrix");

	ViewMatrix = lookAt(
						vec3(0.0, 2.0, 4.0),	//eye
						vec3(0.0 ,0.0 , 0.0),   //direction
						vec3(0.0, 1.0, 0.0)	 //up
						);
	glUniformMatrix4fv(ViewMatrixUniformLocation, 1, GL_FALSE, value_ptr(ViewMatrix));
	ExitOnGLError("ERROR: Could not set the view matrix");

	ProjectionMatrix = perspective(45.0f, (float) CurrentWidth / CurrentHeight , 0.1f, 100.0f);
	glUniformMatrix4fv(ProjectionMatrixUniformLocation, 1, GL_FALSE, value_ptr(ProjectionMatrix));
	ExitOnGLError("ERROR: Could not set the projection matrix");
	glUniform1i(Tex0Loc, 0);
	mesh->Draw();
	glUseProgram(0);
}

Shader.cpp

void Shader::Load(const char* filename)
{
ifstream in(filename, ios::binary);
if(!in)
	{
		cerr << "Could not open the file" << filename << endl;	// Lanzamos un mensaje de error
		exit(1);	// exit(1) usado para abortar el programa
	}
	//Leemos los datos
	std::string glsl_source((std::istreambuf_iterator<char>(in)),
							std::istreambuf_iterator<char>());
	// Terminamos de leer el documento
	in.close();
	//miramos si hay algo
	if(glsl_source.length() == 0)
	{
		cerr<<"ERROR: Any data in the file"<<endl;
		exit(1);
	}
	std::string fs_shader = "#version 330\n #define COMPILING_FS\n" + glsl_source;
	std::string vs_shader = "#version 330\n #define COMPILING_VS\n" + glsl_source;
	// Creamos el programa
	ID = glCreateProgram();
	fragmentShaderID = CreateShader(fs_shader,GL_FRAGMENT_SHADER);
	vertexShaderID = CreateShader(vs_shader,GL_VERTEX_SHADER);
	Initialize();
}

GLuint Shader::CreateShader(std::string shader, GLenum type_shader)
{
	GLuint shader_id = 0;
	const char* glsl_cstr;
	shader_id = glCreateShader(type_shader);
	glShaderSource(shader_id, 1, &(glsl_cstr=shader.c_str()),NULL);
	glCompileShader(shader_id);
	ExitOnGLError("Could not compile the shader");
	CheckCompile(shader_id);
	return shader_id;
}

void Shader::Initialize(void)
{
    glAttachShader(ID, fragmentShaderID);
    ExitOnGLError("No se puede vincular el Fragment Shader");
    glAttachShader(ID, vertexShaderID);
    ExitOnGLError("No se puede vincular el Vertex Shader");
    glLinkProgram(ID);
    ExitOnGLError("No se puede conectar al programa");
    CheckLink(ID);
}

GLint Shader::GetUniformLocation(const char* param)
{
	return glGetUniformLocation(ID, param);
}

void CheckCompile(GLuint id)
{
	GLint compiled = 0;
	GLint length = 0;
	glGetShaderiv(id, GL_COMPILE_STATUS, &compiled);
	if(compiled == 0)
	{
		std::cerr<<"ERROR: The shader´s compilation fail"<<std::endl;
		glGetShaderiv(id, GL_INFO_LOG_LENGTH, &length);
		if(length > 1) {
		 std::string log(length, '\0');
		 glGetShaderInfoLog(id, length, &length, &log[0]);
		 std::cerr<<log<<std::endl;
		 exit(1);
		}
	}else
	{
		std::cout<<"The shader´s compilation was successfully"<<std::endl;
	}
}

void CheckLink(GLuint id)
{
	//CheckAndLog(id,GL_LINK_STATUS,"conexion");
	GLint compiled = 0;
	GLint length = 0;
	glGetProgramiv(id, GL_LINK_STATUS, &compiled);
	if(compiled == 0)
	{
		std::cerr<<"ERROR: The linking fail"<<std::endl;
		glGetProgramiv(id, GL_INFO_LOG_LENGTH, &length);
		if(length > 1) {
		 std::string log(length, '\0');
		 glGetProgramInfoLog(id, length, &length, &log[0]);
		 std::cerr<<log<<std::endl;
		 exit(1);
		}
	}else
	{
		std::cout<<"The linking was successfully"<<std::endl;
	}
}

Edited by ShotoReaper, 14 October 2012 - 08:25 AM.

[Brother Bob]

Have you implemented proper copy or move semantics for your shader objects?

[ShotoReaper]

Sorry, I can´t understand your question.What do you mean exactly?

[Brother Bob]

In Engine::CreateMesh you're creating the shader and returning it by value. This means the shader object has to be copied from the function content.Load<Shader>() to the object shader. If you have not written a proper constructors, an assignment operator and a destructor to treat the object as a value, you cannot use the shader object as if it was a value either but that is what you're currently doing.

Look up the Rule of Three; here's a clicky for an example.