On Apr 17, 2013, at 7:06 PM, Greg Parker <gpar...@apple.com> wrote: > On Apr 17, 2013, at 4:14 PM, Quincey Morris > <quinceymor...@rivergatesoftware.com> wrote: > >> I'm not sure if this is the right list for this, but then I'm not sure what >> is the right list. >> >> I'm seeing a consistent problem disposing of GCD semaphores. For example, if >> I create a semaphore like this: >> >> semaphore = dispatch_semaphore_create (10); >> >> and then use if for a while, then try to destroy it (using ARC): >> >> semaphore = nil; >> >> If the semaphore's count is less than the original value (10 in the >> example), I get a EXC_BAD_INSTRUCTION crash. >> >> It's not clear to me why it should matter whether the original count has >> been restored. There's nothing waiting on the semaphore -- the operations >> that decremented the count have themselves be disposed of already. >> >> If I forcibly increment the count to 10 *or more*, there's no crash. > > dispatch assumes you are using the semaphore in a lock-like pattern, where > all waiters are expected to signal when they are done with their work. In > that pattern, destroying a semaphore whose value is less than its original > value indicates a bug somewhere (because somebody should have signaled the > semaphore but has not yet done so). _dispatch_semaphore_dispose() is > enforcing that assumption and deliberately halting your process if it fails.
Then why not use something like an assertion or an exception which could actually let the user / developer know why you crashed, instead of just EXC_BAD_INSTRUCTION? Charles _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
