In C and C++ is there a cross-platform way of yielding a thread? Something like sched_yield() or Sleep(0)? Does SDL_Delay(0) always yield or will it return immediately in some implementations?
Given that neither C nor C++ (up to C++98) has "threads," there is no fully cross-platform way for a thread to yield.
In C++0x, there is a function std::this_thread::yield() that can be called to yield. That will be the portable way for a thread to yield, once people start using the C++0x threads library.
in the c++ case, boost::thread::yield() does what you ask. On platforms with posix threads, pthread_yield() performs the same function for C and anything that links with it. On platforms where this doesn't immediately stop the thread and start another, it's because the scheduler doesn't support that functionality. I don't think that many such platforms actually exist in the wild.
来源：https://stackoverflow.com/questions/4282773/cross-platform-way-of-yielding-a-thread-in-c-c