Xcode 8 not printing exception reason

You're not alone. It's happening to me too, and I'm disappointed nobody has responded to this.

I guessed that it was because I was frankensteining my Xcode 8 app to add the SDK from Xcode 7, but I've since (finally) made to upgrade to Swift 3 / iOS10 SDK and have reinstalled Xcode.app from scratch. And today I found that the missing reason log is still happening.

I've resorted to opening the system log in the Devices window, wading through the spam to find the crash report which does include the explanation. (which intersects another long-standing "bug", the number of lines logged to that window from an ios device makes it rather unusable).

(which intersects another long-standing "bug", the number of lines logged to that window from an ios device makes it rather unusable)

Console app has really good filtering support. If there’s some specific log entry you want to look for, I recommend that you set up and save a filter for that so you can quickly go back to it in the future. For examples of this, watch the demo in WWDC 2016 Session 721 Unified Logging and Activity Tracing.

Notwithstanding the above, it is weird that your Xcode isn’t displaying uncaught exceptions. My recommendation is that you create a new test project, configure it to force an exception, and see if that reproduces the problem. I did this (my table view controller code is pasted in below) and I definitely see the expected exception backtrace.

If you continue to see the problem in your main app but don’t see it in your test app then you know that it’s something to do with how your main app is set up. The first thing I’d look at there is third-party crash reporters. If you’re using one, you should temporarily remove it to see if that changes things.

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import UIKit

class MainViewController : UITableViewController {

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 5
    }

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        return tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
    }

    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        tableView.insertRows(at: [IndexPath(row: 0, section: 0)], with: .none)
        tableView.deselectRow(at: indexPath, animated: true)
    }
}

I just had this problem with XCode 9.

Becase I was getting way too many console messages, I set the scheme environment variable OS_ACTIVITY_MODE to "disable". Removing this variable, I was able to get the exception stacktrace to print again. (Among all the other ******* the OS was spewing out.)

Thought I'd reply to this, even though the original posting was a couple years ago, since there weren't any other solutions posted.