On 5/3/17 10:41 PM, Eric Griffis wrote:
Hello,
I'm having trouble catching "terminate break" exceptions when combining
break-thread with thread-wait.
MWE 1:
(with-handlers ([exn:break:terminate? writeln])
(let ([t (thread (lambda () (thread-wait (current-thread))))])
(break-thread t 'terminate)
(thread-wait t)))
Threads do not inherit exception handlers. You need to move the
`with-handlers` to the new thread:
(let ([t (thread (lambda ()
(with-handlers ([exn:break:terminate? writeln])
(thread-wait (current-thread)))))])
(break-thread t 'terminate)
(thread-wait t))
Except that isn't quite right either, because , the main thread might
(very likely) send the break to `t` before `t` is ready to catch it. So
we need some additional synchronization:
(define t-ready (make-semaphore 0))
(let ([t (thread (lambda ()
(with-handlers ([exn:break:terminate? writeln])
(semaphore-post t-ready)
(thread-wait (current-thread)))))])
(semaphore-wait t-ready)
(break-thread t 'terminate)
(thread-wait t))
That version should reliably print out the break exception.
Ryan
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