-int getcontext(ucontext_t *);
-void makecontext(ucontext_t *, void (*)(void), int, ...);
-int setcontext(const ucontext_t *);
-int swapcontext(ucontext_t *, const ucontext_t *);
+struct __ucontext;
+
+int getcontext(struct __ucontext *);
+void makecontext(struct __ucontext *, void (*)(void), int, ...);
+int setcontext(const struct __ucontext *);
+int swapcontext(struct __ucontext *, const struct __ucontext *);