fix: Crash in AppHangs when no threads (#2725)

Fix a crash (index 0 beyond bounds for empty array) in the AppHangs logic when creating the app hang event, and the SDK can't retrieve threads by not reporting an AppHang in such a case. Fixes GH-2713
getsentry · Feb 27, 2023 · 28333b6 · 28333b6
1 parent efb2222
commit 28333b6
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased 
+
+### Fixes
+
+- Crash in AppHangs when no threads (#2725)
+
 ## 8.2.0
 
 ### Features

diff --git a/Sources/Sentry/SentryANRTrackingIntegration.m b/Sources/Sentry/SentryANRTrackingIntegration.m
@@ -8,6 +8,7 @@
 #import "SentryEvent.h"
 #import "SentryException.h"
 #import "SentryHub+Private.h"
+#import "SentryLog.h"
 #import "SentryMechanism.h"
 #import "SentrySDK+Private.h"
 #import "SentryStacktrace.h"
@@ -58,11 +59,16 @@ - (void)anrDetected
 {
     SentryThreadInspector *threadInspector = SentrySDK.currentHub.getClient.threadInspector;
 
-    NSString *message = [NSString stringWithFormat:@"App hanging for at least %li ms.",
-                                  (long)(self.options.appHangTimeoutInterval * 1000)];
-
     NSArray<SentryThread *> *threads = [threadInspector getCurrentThreadsWithStackTrace];
 
+    if (threads.count == 0) {
+        SENTRY_LOG_WARN(@"Getting current thread returned an empty list. Can't create AppHang "
+                        @"event without a stacktrace.");
+        return;
+    }
+
+    NSString *message = [NSString stringWithFormat:@"App hanging for at least %li ms.",
+                                  (long)(self.options.appHangTimeoutInterval * 1000)];
     SentryEvent *event = [[SentryEvent alloc] initWithLevel:kSentryLevelError];
     SentryException *sentryException = [[SentryException alloc] initWithValue:message
                                                                          type:@"App Hanging"];

diff --git a/Tests/SentryTests/Integrations/ANR/SentryANRTrackingIntegrationTests.swift b/Tests/SentryTests/Integrations/ANR/SentryANRTrackingIntegrationTests.swift
@@ -98,6 +98,15 @@ class SentryANRTrackingIntegrationTests: SentrySDKIntegrationTestsBase {
             XCTAssertTrue(threadsWithFrames > 1, "Not enough threads with frames")
         }
     }
+
+    func testANRDetected_ButNoThreads_EventNotCaptured() {
+        givenInitializedTracker()
+        setUpThreadInspector(addThreads: false)
+
+        Dynamic(sut).anrDetected()
+
+        assertNoEventCaptured()
+    }
 
     private func givenInitializedTracker(isBeingTraced: Bool = false) {
         givenSdkWithHub()
@@ -106,27 +115,32 @@ class SentryANRTrackingIntegrationTests: SentrySDKIntegrationTestsBase {
         sut.install(with: self.options)
     }
 
-    private func setUpThreadInspector() {
+    private func setUpThreadInspector(addThreads: Bool = true) {
         let threadInspector = TestThreadInspector.instance
 
-        let frame1 = Sentry.Frame()
-        frame1.function = "Second_frame_function"
-
-        let thread1 = SentryThread(threadId: 0)
-        thread1.stacktrace = SentryStacktrace(frames: [frame1], registers: [:])
-        thread1.current = true
-
-        let frame2 = Sentry.Frame()
-        frame2.function = "main"
-
-        let thread2 = SentryThread(threadId: 1)
-        thread2.stacktrace = SentryStacktrace(frames: [frame2], registers: [:])
-        thread2.current = false
-
-        threadInspector.allThreads = [
-            thread2,
-            thread1
-        ]
+        if addThreads {
+
+            let frame1 = Sentry.Frame()
+            frame1.function = "Second_frame_function"
+
+            let thread1 = SentryThread(threadId: 0)
+            thread1.stacktrace = SentryStacktrace(frames: [frame1], registers: [:])
+            thread1.current = true
+
+            let frame2 = Sentry.Frame()
+            frame2.function = "main"
+
+            let thread2 = SentryThread(threadId: 1)
+            thread2.stacktrace = SentryStacktrace(frames: [frame2], registers: [:])
+            thread2.current = false
+
+            threadInspector.allThreads = [
+                thread2,
+                thread1
+            ]
+        } else {
+            threadInspector.allThreads = []
+        }
 
         SentrySDK.currentHub().getClient()?.threadInspector = threadInspector
     }

diff --git a/Tests/SentryTests/SentrySDKIntegrationTestsBase.swift b/Tests/SentryTests/SentrySDKIntegrationTestsBase.swift
@@ -33,6 +33,14 @@ class SentrySDKIntegrationTestsBase: XCTestCase {
         SentrySDK.setCurrentHub(SentryHub(client: nil, andScope: nil))
     }
 
+    func assertNoEventCaptured() {
+        guard let client = SentrySDK.currentHub().getClient() as? TestClient else {
+            XCTFail("Hub Client is not a `TestClient`")
+            return
+        }
+        XCTAssertEqual(0, client.captureEventInvocations.count, "No event should be captured.")
+    }
+
     func assertEventCaptured(_ callback: (Event?) -> Void) {
         guard let client = SentrySDK.currentHub().getClient() as? TestClient else {
             XCTFail("Hub Client is not a `TestClient`")