Syntax error in OpenGl shader that is copied from YouTube - c++

Question

I trying to learn OpenGl and now I wanted to make a simple red triangle on a black background with vertices and shaders. I copied the code from that YouTube video. I've changed a view things. That's my code:
#include "prec.h"
struct Vector2
{
float x, y;
};
struct TrianglePos
{
Vector2 a, b, c;
};
static unsigned int CompileShader(unsigned int type, const std::string& source)
{
unsigned int id = glCreateShader(type);
const char* src = source.c_str();
glShaderSource(id, 1, &src, nullptr);
glCompileShader(id);
int result;
glGetShaderiv(id, GL_COMPILE_STATUS, &result);
if (!result)
{
int length;
glGetShaderiv(id, GL_INFO_LOG_LENGTH, &length);
char* message = (char*)alloca(length * sizeof(char));
glGetShaderInfoLog(id, length, &length, message);
std::cout << "Failed to compile shader, message: " << message << std::endl;
glDeleteShader(id);
return 0;
}
return id;
}
static unsigned int createShader(const std::string& vertexShader, const std::string& fragmentShader)
{
unsigned int program = glCreateProgram();
unsigned int vs = CompileShader(GL_VERTEX_SHADER, vertexShader);
unsigned int fs = CompileShader(GL_FRAGMENT_SHADER, fragmentShader);
glAttachShader(program, vs);
glAttachShader(program, fs);
glLinkProgram(program);
glValidateProgram(program);
glDeleteShader(vs);
glDeleteShader(fs);
return program;
}
int main() {
if (!glfwInit())
return -1;
GLFWwindow *window = glfwCreateWindow(640, 480, "Sand Box GL", NULL, NULL);
if (!window) {
std::cout << "problems with window" << std::endl;
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
glewExperimental = GL_TRUE;
if (GLEW_OK != glewInit()) {
std::cout << "something with glew went wrong" << std::endl;
return -1;
}
TrianglePos trianglePos = {
-0.5f, -0.5f,
0.0f, 0.5f,
0.5f, -0.5f
};
unsigned int buffer;
glGenBuffers(1, &buffer);
glBindBuffer(GL_ARRAY_BUFFER, buffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(trianglePos), &trianglePos, GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, sizeof(Vector2), 0);
std::string vertexShader =
"#version 400 core\n"
"\n"
"layout(location = 0) in vec4 position;\n"
"\n"
"void main() \n"
"{\n"
" gl_Position = position;\n"
"}\n";
std::string fragmentShader =
"#version 400 core\n"
"\n"
"layout(location = 0) out vec4 color;\n"
"\n"
"void main()\n"
"{\n"
" color = vec4(1.0, 0.0, 0.0, 1.0);\n"
"}\n";
const char *versionGL;
versionGL = (char *) (glGetString(GL_VERSION));
std::cout << "openGl version: " << versionGL << std::endl;
if(GL_VERSION_4_0)
std::cout << "opengl 4.0 supported" << std::endl;
unsigned int shader = createShader(vertexShader, fragmentShader);
glUseProgram(shader);
while (!glfwWindowShouldClose(window)) {
glClear(GL_COLOR_BUFFER_BIT);
glDrawArrays(GL_TRIANGLES, 0, 3);
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwTerminate();
return 0;
}
and that's the precompiled header (prec.h): #pragma once
#ifndef GLEWINIT_PREC_H
#define GLEWINIT_PREC_H
#endif //GLEWINIT_PREC_H
#include "GL/glew.h"
#include <GLFW/glfw3.h>
#include <iostream>
the program prints that to the console ("OpenGL 4.0 supported" means that GL_VERSION_4_0 == true):
openGl version: 2.1 INTEL-14.5.22
opengl 4.0 supported
When I try to run it I get this error message from the shader Compiler for my vertex and fragment shader:
ERROR: 0:1: '' : version '400' is not supported
ERROR: 0:1: '' : syntax error: #version
ERROR: 0:3: 'layout' : syntax error: syntax error
When I change the #version 400 core to #version 120 I only get the syntax error for the layout. Because of that I think I messed up something with glew. What could I try?

Answer 1

Your system does not support OpenGL 4.0. It just supports OpenGL 2.1. See the output
openGl version: 2.1 INTEL-14.5.22
GLSL 1.20 corresponds to OpenGL 2.1. Downgrade the shader:
Vertex shader
#version 120
attribute vec4 position;
void main()
{
gl_Position = position;
}
Fragment shader
#version 120
void main()
{
gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
}
Respectively using Raw string literals (C++11):
std::string vertexShader =
R"(#version 120
attribute vec4 position;
void main()
{
gl_Position = position;
}
)";
std::string fragmentShader =
R"(#version 120
void main()
{
gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
}
)";