+std::string read_file(const std::string &filename);
+GLhandleARB compile_shader(const std::string &shader_src, GLenum type);
+
+#ifdef NDEBUG
+#define check_error()
+#else
+#define check_error() { int err = glGetError(); if (err != GL_NO_ERROR) { printf("GL error 0x%x at %s:%d\n", err, __FILE__, __LINE__); exit(1); } }
+#endif
+