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[PLAT-6261] Detect uncaught objc exceptions on Mac Catalyst and iOSAppOnMac #1053

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Mar 29, 2021
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[PLAT-6261] Detect uncaught objc exceptions on Mac Catalyst and iOSAppOnMac #1053

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2613411
Detect uncaught objc exceptions on Mac Catalyst and iOSAppOnMac
nickdowell Mar 26, 2021
bc0a3eb
Mention FB8901200 in comment
nickdowell Mar 29, 2021
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68 changes: 68 additions & 0 deletions Bugsnag/KSCrash/Source/KSCrash/Recording/Sentry/BSG_KSCrashSentry_NSException.m
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,8 @@
//#define BSG_KSLogger_LocalLevel TRACE
#import "BSG_KSLogger.h"

#import <objc/runtime.h>

// ============================================================================
#pragma mark - Globals -
// ============================================================================
Expand Down Expand Up @@ -130,9 +132,54 @@ void bsg_recordException(NSException *exception) {

BSG_KSLOG_DEBUG(@"Calling main crash handler.");
bsg_g_context->onCrash(crashContext());

bsg_kscrashsentry_resumeThreads();
}
}

// ============================================================================
#pragma mark - iOS apps on macOS -
// ============================================================================

// iOS apps behave a little differently when running on macOS via Catalyst or
// on Apple Silicon. Uncaught NSExceptions raised while handling UI events get
// caught by AppKit and are not propagated to NSUncaughtExceptionHandler or
// std::terminate_handler (reported to Apple: FB8901200) therefore we need
// another way to detect them...

#if TARGET_OS_IOS

static Method NSApplication_reportException;

/// Pointer to the real implementation of -[NSApplication reportException:]
static void (* NSApplication_reportException_imp)(id, SEL, NSException *);

/// Overrides -[NSApplication reportException:]
static void bsg_reportException(id self, SEL _cmd, NSException *exception) {
BSG_KSLOG_DEBUG(@"reportException: %@", exception);

bsg_kscrashsentry_beginHandlingCrash(bsg_g_context);

bsg_recordException(exception);

#if TARGET_OS_MACCATALYST
// Mac Catalyst apps continue to run after an uncaught exception is thrown
// while handling a UI event. Our crash sentries should remain installed to
// catch any subsequent unhandled exceptions or crashes.
#else
// iOS apps running on Apple Silicon Macs terminate with an EXC_BREAKPOINT
// mach exception. We don't want to catch that because its stack trace will
// not point to where the exception was raised (its top frame will be
// -[NSApplication _crashOnException:]) so we should uninstall our crash
// sentries.
bsg_kscrashsentry_uninstall(BSG_KSCrashTypeAll);
#endif

NSApplication_reportException_imp(self, _cmd, exception);
}

#endif

// ============================================================================
#pragma mark - API -
// ============================================================================
Expand All @@ -153,6 +200,18 @@ bool bsg_kscrashsentry_installNSExceptionHandler(
BSG_KSLOG_DEBUG(@"Setting new handler.");
NSSetUncaughtExceptionHandler(&bsg_ksnsexc_i_handleException);

#if TARGET_OS_IOS
NSApplication_reportException =
class_getInstanceMethod(NSClassFromString(@"NSApplication"),
NSSelectorFromString(@"reportException:"));
if (NSApplication_reportException) {
BSG_KSLOG_DEBUG(@"Overriding -[NSApplication reportException:]");
NSApplication_reportException_imp = (void *)
method_setImplementation(NSApplication_reportException,
(IMP)bsg_reportException);
}
#endif

return true;
}

Expand All @@ -164,5 +223,14 @@ void bsg_kscrashsentry_uninstallNSExceptionHandler(void) {

BSG_KSLOG_DEBUG(@"Restoring original handler.");
NSSetUncaughtExceptionHandler(bsg_g_previousUncaughtExceptionHandler);

#if TARGET_OS_IOS
if (NSApplication_reportException && NSApplication_reportException_imp) {
BSG_KSLOG_DEBUG(@"Restoring original -[NSApplication reportException:]");
method_setImplementation(NSApplication_reportException,
(IMP)NSApplication_reportException_imp);
}
#endif

bsg_g_installed = 0;
}
7 changes: 7 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
@@ -1,6 +1,13 @@
Changelog
=========

## TBD

### Bug fixes

* Uncaught exceptions thrown while handing UI events in iOS apps running on macOS are now detected.
[#1053](https://github.com/bugsnag/bugsnag-cocoa/pull/1053)

## 6.8.1 (2021-03-24)

### Bug fixes
Expand Down