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During the dynamic extent of the signaling process for a particular condition object, signaling the same condition object again is permitted if and only if the situation represented in both cases are the same.
For example, a handler might legitimately signal the condition object that is its argument in order to allow outer handlers first opportunity to handle the condition. (Such a handlers is sometimes called a “default handler.”) This action is permitted because the situation which the second signaling process is addressing is really the same situation.
On the other hand, in an implementation that implemented asynchronous keyboard events by interrupting the user process with a call to signal, it would not be permissible for two distinct asynchronous keyboard events to signal identical condition objects at the same time for different situations.