+struct gstr {
+ size_t len;
+ char *s;
+};
+struct gstr str_new(void);
+struct gstr str_assign(const char *s);
+void str_free(struct gstr *gs);
+void str_append(struct gstr *gs, const char *s);
+void str_printf(struct gstr *gs, const char *fmt, ...);
+const char *str_get(struct gstr *gs);
+