A couple of wrappers for opengl which are handy when you want to provide some openGL features in your library. Simply embed these into your cpp file. (Note that your executable will become slightly bigger because of this.)

opengl_wrappers.c

/*
 
 See https://gist.github.com/roxlu/6152fccfdd0446533e1b for the latest version.
 
 Author: roxlu
 Twitter: http://www.twitter.com/roxlu 

*/

/* ------------------------------------------------------------------------*/
/* Embeddable OpenGL wrappers.                                             */
/* ------------------------------------------------------------------------*/
static int create_shader(GLuint* out, GLenum type, const char* src);           /* create a shader, returns 0 on success, < 0 on error. e.g. create_shader(&vert, GL_VERTEX_SHADER, DRAWER_VS); */
static int create_program(GLuint* out, GLuint vert, GLuint frag, int link);    /* create a program from the given vertex and fragment shader. returns 0 on success, < 0 on error. e.g. create_program(&prog, vert, frag, 1); */
static int print_shader_compile_info(GLuint shader);                           /* prints the compile info of a shader. returns 0 when shader compiled, < 0 on error. */
static int print_program_link_info(GLuint prog);                               /* prints the program link info. returns 0 on success, < 0 on error. */
/* ------------------------------------------------------------------------*/


/* ------------------------------------------------------------------------*/
/* Embeddable OpenGL wrappers.                                             */
/* ------------------------------------------------------------------------*/

static int create_shader(GLuint* out, GLenum type, const char* src) {
 
  *out = glCreateShader(type);
  glShaderSource(*out, 1, &src, NULL);
  glCompileShader(*out);
  
  if (0 != print_shader_compile_info(*out)) {
    *out = 0;
    return -1;
  }
  
  return 0;
}

/* create a program, store the result in *out. when link == 1 we link too. returns -1 on error, otherwise 0 */
static int create_program(GLuint* out, GLuint vert, GLuint frag, int link) {
  *out = glCreateProgram();
  glAttachShader(*out, vert);
  glAttachShader(*out, frag);

  if(1 == link) {
    glLinkProgram(*out);
    if (0 != print_program_link_info(*out)) {
      *out = 0;
      return -1;
    }
  }

  return 0;
}

/* checks + prints program link info. returns 0 when linking didn't result in an error, on link erorr < 0 */
static int print_program_link_info(GLuint prog) {
  GLint status = 0;
  GLint count = 0;
  GLchar* error = NULL;
  GLsizei nchars = 0;

  glGetProgramiv(prog, GL_LINK_STATUS, &status);
  if(status) {
    return 0;
  }

  glGetProgramiv(prog, GL_INFO_LOG_LENGTH, &count);
  if(count <= 0) {
    return 0;
  }

  error = (GLchar*)malloc(count);
  glGetProgramInfoLog(prog, count, &nchars, error);
  if (nchars <= 0) {
    free(error);
    error = NULL;
    return -1;
  }

  printf("\nPROGRAM LINK ERROR");
  printf("\n--------------------------------------------------------\n");
  printf("%s", error);
  printf("--------------------------------------------------------\n\n");

  free(error);
  error = NULL;
  return -1;
}

/* checks the compile info, if it didn't compile we return < 0, otherwise 0 */
static int print_shader_compile_info(GLuint shader) {

  GLint status = 0;
  GLint count = 0;
  GLchar* error = NULL;

  glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
  if(status) {
    return 0;
  }
  
  glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &count);
  if (0 == count) {
    return 0;
  }

  error = (GLchar*) malloc(count);
  glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &count);
  if(count <= 0) {
    free(error);
    error = NULL;
    return 0;
  }

  glGetShaderInfoLog(shader, count, NULL, error);
  printf("\nSHADER COMPILE ERROR");
  printf("\n--------------------------------------------------------\n");
  printf("%s", error);
  printf("--------------------------------------------------------\n\n");

  free(error);
  error = NULL;
  return -1;
}

/* ------------------------------------------------------------------------*/