Syntax error in OpenGl shader that is copied from YouTube

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);
}
)";