Exception state can be saved to incorrect thread in 1.88

[zhykzhykzhyk]

The manage_exception_state try to save and restore the exception state from/to the current thread that executing the fiber, but only one __cxa_get_globals() call is generated for the outer function after optimization, which would be incorrect if fiber resume on another thread.

context/include/boost/context/fiber_fcontext.hpp

Lines 88 to 98 in 6ff80e0

	class manage_exception_state {
	public:
	manage_exception_state() {
	exception_state_ = *__cxa_get_globals();
	}
	~manage_exception_state() {
	*__cxa_get_globals() = exception_state_;
	}
	private:
	__cxa_eh_globals exception_state_;
	};

Result from compiler explorer

// check disassembly of this function
void foo(boost::context::fiber&& f) { std::move(f).resume(); }