The current exception-handling implementation is safe for multithreading because exceptions in one thread do not interfere with exceptions in other threads. However, you cannot use exceptions to communicate across threads because an exception thrown from one thread cannot be caught in another.
Each thread can set its own terminate() or unexpected() function. Calling set_terminate() or set_unexpected() in one thread affects only the exceptions in that thread. The default function for terminate() is abort() for any thread (see Specifying Runtime Errors).
Thread cancellation through a call to pthread_cancel(3T) results in the destruction of automatic (local nonstatic) objects on the stack except when you specify -noex or -features=no%except.
pthread_cancel(3T) uses the same mechanism as exceptions. When a thread is cancelled, the execution of local destructors is interleaved with the execution of cleanup routines that the user has registered with pthread_cleanup_push(). The local objects for functions called after a particular cleanup routine is registered are destroyed before that routine is executed.