+ if (!gl_CreateShader || !gl_ShaderSource || !gl_CompileShader || !gl_CreateProgram || !gl_AttachShader || !gl_LinkProgram || !gl_UseProgram || !gl_GetShaderiv || !gl_GetShaderInfoLog || !gl_GetProgramiv || !gl_GetProgramInfoLog || !gl_GetAttribLocation || !gl_VertexAttribPointer || !gl_EnableVertexAttribArray || !gl_GetUniformLocation || !gl_UniformMatrix4fv)
+ {
+ fprintf (stderr, "glCreateShader, glShaderSource, glCompileShader, glCreateProgram, glAttachShader, glLinkProgram, glUseProgram, glGetShaderiv, glGetShaderInfoLog, glGetProgramiv, glGetProgramInfoLog, glGetAttribLocation, glVertexAttribPointer, glEnableVertexAttribArray, glGetUniformLocation or glUniformMatrix4fv not found");
+ exit(1);
+ }