Question

I compiled the following code:

// Triangle.cpp
// Our first OpenGL program that will just draw a triangle on the screen.

#include <GLTools.h>            // OpenGL toolkit
#include <GLShaderManager.h>    // Shader Manager Class

#ifdef __APPLE__
#include <glut/glut.h>          // OS X version of GLUT
#else
#define FREEGLUT_STATIC
#include <GL/glut.h>            // Windows FreeGlut equivalent
#endif

GLBatch triangleBatch;
GLShaderManager shaderManager;

///////////////////////////////////////////////////////////////////////////////
// Window has changed size, or has just been created. In either case, we need
// to use the window dimensions to set the viewport and the projection matrix.
void ChangeSize(int w, int h)
    {
    glViewport(0, 0, w, h);
    }


///////////////////////////////////////////////////////////////////////////////
// This function does any needed initialization on the rendering context. 
// This is the first opportunity to do any OpenGL related tasks.
void SetupRC()
    {
    // Blue background
    glClearColor(0.0f, 0.0f, 1.0f, 1.0f );

    shaderManager.InitializeStockShaders();

    // Load up a triangle
    GLfloat vVerts[] = { -0.5f, 0.0f, 0.0f, 
                          0.5f, 0.0f, 0.0f,
                          0.0f, 0.5f, 0.0f };

    triangleBatch.Begin(GL_TRIANGLES, 3);
    triangleBatch.CopyVertexData3f(vVerts);
    triangleBatch.End();
    }



///////////////////////////////////////////////////////////////////////////////
// Called to draw scene
void RenderScene(void)
    {
    // Clear the window with current clearing color
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

    GLfloat vRed[] = { 1.0f, 0.0f, 0.0f, 1.0f };
    shaderManager.UseStockShader(GLT_SHADER_IDENTITY, vRed);
    triangleBatch.Draw();

    // Perform the buffer swap to display back buffer
    glutSwapBuffers();
    }


///////////////////////////////////////////////////////////////////////////////
// Main entry point for GLUT based programs
int main(int argc, char* argv[])
    {
    gltSetWorkingDirectory(argv[0]);

    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH | GLUT_STENCIL);
    glutInitWindowSize(800, 600);
    glutCreateWindow("Triangle");
    glutReshapeFunc(ChangeSize);
    glutDisplayFunc(RenderScene);

    GLenum err = glewInit();
    if (GLEW_OK != err) {
        fprintf(stderr, "GLEW Error: %s\n", glewGetErrorString(err));
        return 1;
        }

    SetupRC();

    glutMainLoop();
    return 0;
    }

But when i try to execute it the program crash, then the debugger gives me the following error:

Excepción no controlada en 0x00000000 en Triangle.exe: 0xC0000005: Infracción de acceso al leer la ubicación 0x00000000.

Answer 1

To use glCreateShader(GL_VERTEX_SHADER) you must be running OpenGL 2.0 or higher. One way to tell is to check the value of GLEW_VERSION_2_0 (after your call to glewInit()). If the value is true then OpenGL 2.0 is supported. Otherwise, you may need to update your graphics driver or use a newer graphics card.