Style::onSpriteError is apparently sometimes called with a null exception_ptr

[jfirebaugh]

Style::onSpriteError, and probably other on*Error methods, are apparently sometimes called with a null std::exception_ptr. This conclusion is based primarily on the fact that adding a guard clause for this solved the crash in #4330.

We expect on*Error methods to be called only when there is a legitimate error to report, so something is off here and needs to be investigated.

This may also be the root cause of the mysterious crashes reported in #3280. (If so, it would be a relief to know that the cause isn't related to RTTI.)

[jfirebaugh]

I'm not seeing how this is possible, unless there's a libc++ bug. Either std::make_exception_ptr would have to return a null std::exception_ptr, or std::current_exception() would, when called inside a catch block.

[jfirebaugh]

Some log output from when this occurs, from #4382 (comment):

W/com.mapbox.mapboxsdk.http.HTTPRequest(14356): [HTTP] Request could not be executed: Failed to connect to /192.168.0.4:8080
W/com.mapbox.mapboxsdk.http.HTTPRequest(14356): [HTTP] Request could not be executed: Failed to connect to /192.168.0.4:8080
E/mbgl    (14356): {Map}[Setup]: loading style failed: Failed to connect to /192.168.0.4:8080
E/mbgl    (14356): {Map}[Style]: Failed to load sprite: (null)
E/mbgl    (14356): {Map}[Style]: Failed to load sprite: (null)

[brunoabinader]

I grabbed a similar situation while running the Android test app via simulator. Unfortunately I can't reproduce the issue anymore after upgrading my Android Studio, but I was using a x86 build running on a x86_64 simulator environment - Nexus 4 API 22 (Android 5.1.1). I got the following output when trying to open any of the activities from the test app:

com.mapbox.mapboxsdk.testapp A/libc: ../../include/mbgl/util/string.hpp:38: std::string mbgl::util::toString(std::exception_ptr): assertion "error" failed
com.mapbox.mapboxsdk.testapp A/libc: Fatal signal 6 (SIGABRT), code -6 in tid 3038 ()

[stale]

This issue has been automatically detected as stale because it has not had recent activity and will be archived. Thank you for your contributions.