The pthread_cancel function requests that thread be canceled. The target threads cancelability state and type determines when the cancellation takes effect. When the cancellation is acted on, the cancellation cleanup handlers for thread are called. When the last cancellation cleanup handler returns, the thread-specific data destructor functions will be called for thread. When the last destructor function returns, thread will be terminated.
The cancellation processing in the target thread runs asynchronously with respect to the calling thread returning from pthread_cancel.
A status of PTHREAD_CANCELED is made available to any threads joining with the target. The symbolic constant PTHREAD_CANCELED expands to a constant expression of type "(void *)", whose value matches no pointer to an object in memory nor the value NULL.
If successful, the pthread_cancel functions will return zero. Otherwise an error number will be returned to indicate the error.
The pthread_cancel function will fail if: