Calling reset before a Javascript method returns causes a crash.

[lanephillips]

Here's the scenario:

1. Objective-C code calls callHandler:data:responseCallback: on WebViewJavascriptBridge.
2. WebViewJavascriptBridge puts the callback in a dictionary with key objc_cb_1.
3. Objective-C code calls reset on the bridge.
4. WebViewJavascriptBridge sets its callback counter back to 0 and clears the callback dictionary.
5. Objective-C code calls callHandler:data:responseCallback: on WebViewJavascriptBridge.
6. WebViewJavascriptBridge puts the callback in a dictionary with key objc_cb_1.
7. The javascript function named in step 1 finishes. (My understanding of how WebViewJavascriptBridge works on the javascript side may be a bit fuzzy, but I'm pretty confident about the Objective-C side.)
8. WebViewJavascriptBridge looks up the callback with key objc_cb_1 (which is actually the callback from step 5), calls it, and removes it from the dictionary.
9. The javascript function named in step 5 finishes.
10. WebViewJavascriptBridge looks up the callback with key objc_cb_1, finds a nil pointer and calls it and crashes the app.

Our workaround has been to simply build a new bridge instead of trying to reset an existing one, and that seems to work fine for us.

[marcuswestin]

Good call. I will review whether reset makes sense to keep around, and if not I'll mark it as deprecated.

I love the thoroughness of your bug report. Thanks for that!
-- while mobile

On Thu, Aug 14, 2014 at 10:37 AM, milkllc notifications@github.com
wrote:

Here's the scenario:

1. Objective-C code calls callHandler:data:responseCallback: on WebViewJavascriptBridge.
2. WebViewJavascriptBridge puts the callback in a dictionary with key objc_cb_1.
3. Objective-C code calls reset on the bridge.
4. WebViewJavascriptBridge sets its callback counter back to 0 and clears the callback dictionary.
5. Objective-C code calls callHandler:data:responseCallback: on WebViewJavascriptBridge.
6. WebViewJavascriptBridge puts the callback in a dictionary with key objc_cb_1.
7. The javascript function named in step 1 finishes. (My understanding of how WebViewJavascriptBridge works on the javascript side may be a bit fuzzy, but I'm pretty confident about the Objective-C side.)
8. WebViewJavascriptBridge looks up the callback with key objc_cb_1 (which is actually the callback from step 5), calls it, and removes it from the dictionary.
9. The javascript function named in step 5 finishes.
10. WebViewJavascriptBridge looks up the callback with key objc_cb_1, finds a nil pointer and calls it and crashes the app.

Our workaround has been to simply build a new bridge instead of trying to reset an existing one, and that seems to work fine for us.

Reply to this email directly or view it on GitHub:
#99

[marcuswestin]

Alright, done. Thanks mate.