c++ - I'm trying to draw a triangle using shaders and VBO. Why my program doesn't work? -

i've tried use code drawing triangle using vbo , shaders.

#include "gl.h" #include <stdlib.h> #include <glfw/glfw3.h>  // utility libraries #include "oglshader.h" #include "oglprogram.h" #include "oglcommon.h" #include "shaders.h" #include "oglbuffer.h"  using namespace opengl;  glfwwindow *window; const int window_width = 800; const int window_height = 600;  shader **shaders; program *mainprogram;  int verticescount = 3; float triangle[] = {     0.0f, 0.5f, 0.0f,     0.5f, -0.5f, 0.0f,     -0.5f, -0.5f, 0.0f, }; int indicescount = 3; int indices[] = {     0, 1, 2 }; buffer *verticesbuffer;  void init() {     glviewport(0, 0, window_width, window_height);     glclearcolor(0, 0, 0, 1);      shaders = new opengl::shader*[2];      // code creates , compiles shaders, links shader program     shaders[0] = new opengl::shader(gl_vertex_shader, opengl::vertexshadersource);     shaders[1] = new opengl::shader(gl_fragment_shader, opengl::fragmentshadersource);     mainprogram = new opengl::program(2, shaders);     mainprogram->use(); // use program      vertices_attrib_location = 0;     colors_attrib_location = 1;     glbindattriblocation(mainprogram->getid(), vertices_attrib_location, "ivertex");     glbindattriblocation(mainprogram->getid(), colors_attrib_location, "icolor");      verticesbuffer = new buffer(gl_array_buffer);     verticesbuffer->data(verticescount*3*sizeof(float), triangle, gl_static_draw); }  void deinit() {     delete verticesbuffer;      delete shaders[0];     delete shaders[1];     delete []shaders;     delete mainprogram; }  void display() {     glclear(gl_color_buffer_bit);      glvertexattrib3f(colors_attrib_location, 1, 0, 1);     verticesbuffer->bind();     glenablevertexattribarray(vertices_attrib_location);     glvertexattribpointer(vertices_attrib_location, 3, gl_float, gl_false, 0, nullptr);      gldrawarrays(gl_triangles, 0, 3); }  void update(double deltatime) {  }  int main(int argc, char **argv) {     if (!glfwinit()) {         exit(1);     }     glfwwindowhint(glfw_samples, 1);     glfwwindowhint(glfw_context_version_major, 2);     glfwwindowhint(glfw_context_version_minor, 1);     window = glfwcreatewindow(window_width, window_height, "test", nullptr, nullptr);     if (!window) {         glfwterminate();         exit(exit_failure);     }     glfwmakecontextcurrent(window);     glfwswapinterval(1);     init();      double lasttime = 0.0;     while (!glfwwindowshouldclose(window)) {         display();         double curtime = glfwgettime();         update(curtime - lasttime);         lasttime = curtime;          glfwswapbuffers(window);         glfwpollevents();     }      deinit();     glfwdestroywindow(window);     glfwterminate();      return 0; } 

here shaders:

namespace opengl {  std::string vertexshadersource =     "#version 120\n\     attribute vec3 ivertex;\     attribute vec3 icolor;\     varying vec3 ocolor;\     void main(void)\n\     {\n\         ocolor = icolor;\n\         \n\         gl_position = vec4(ivertex, 1);\n\     }\n\     ";      std::string fragmentshadersource =     "#version 120\n\     varying vec3 ocolor;\     varying vec2 otexcoord;\n\     void main(void)\n\     {\n\         gl_fragcolor = vec4(ocolor, 1);\n\     }\n\     ";  } 

i tried run code both on intel , ati videocards, see on screen empty black window. i'm doing wrong?