[CP-beta]On iOS 27+ devices, manually process lldb stops by vashworth · Pull Request #192814 · flutter/flutter

vashworth · 2026-09-15T16:24:28Z

Issue Link:

What is the link to the issue this cherry-pick is addressing?

#190307

Impact Description:

What is the impact (ex. visual jank on Samsung phones, app crash, cannot ship an iOS app)?
Does it impact development (ex. flutter doctor crashes when Android Studio is installed),
or the shipping of production apps (the app crashes on launch).
This information is for domain experts and release engineers to understand the consequences of saying yes or no to the cherry pick.

Debugging on iOS 27+ occasionally crashes.

Changelog Description:

Explain this cherry pick:

In one line that is accessible to most Flutter developers.
That describes the state prior to the fix.
That includes which platforms are impacted.
See best practices for examples.

< Replace with changelog description here >
[flutter/190307] When debugging on physical iOS 27 devices, app occasionally crashes.

Workaround:

Is there a workaround for this issue?

No

Risk:

What is the risk level of this cherry-pick?

Low
Medium
High

Test Coverage:

Are you confident that your fix is well-tested by automated tests?

Yes
No

Validation Steps:

What are the steps to validate that this fix works?

Use example code a script to reproduce from #190307

On iOS 27+ devices, `lldb` sometimes doesn't stop on breakpoints when auto-continue is enabled. To workaround this, we disable auto-continue and manually process stops. If a stop is caused by a breakpoint, we tell the process to continue. Otherwise, we print the backtrace and detach. Fixes flutter#190307. - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [AI contribution guidelines] and understand my responsibilities, or I am not using AI tools. - [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [x] I signed the [CLA]. - [x] I listed at least one issue that this PR fixes in the description above. - [x] I updated/added relevant documentation (doc comments with `///`). - [x] I added new tests to check the change I am making, or this PR is [test-exempt]. - [x] I followed the [breaking change policy] and added [Data Driven Fixes] where supported. - [x] All existing and new tests are passing. If you need help, consider asking for advice on the #hackers-new channel on [Discord]. If this change needs to override an active code freeze, provide a comment explaining why. The code freeze workflow can be overridden by code reviewers. See pinned issues for any active code freezes with guidance. **Note**: The Flutter team is currently trialing the use of [Gemini Code Assist for GitHub](https://developers.google.com/gemini-code-assist/docs/review-github-code). Comments from the `gemini-code-assist` bot should not be taken as authoritative feedback from the Flutter team. If you find its comments useful you can update your code accordingly, but if you are unsure or disagree with the feedback, please feel free to wait for a Flutter team member's review for guidance on which automated comments should be addressed.  [Contributor Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview [AI contribution guidelines]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#ai-contribution-guidelines [Tree Hygiene]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md [test-exempt]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests [Flutter Style Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md [Features we expect every widget to implement]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement [CLA]: https://cla.developers.google.com/ [flutter/tests]: https://github.com/flutter/tests [breaking change policy]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes [Discord]: https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md [Data Driven Fixes]: https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md

flutter-dashboard · 2026-09-15T16:24:40Z

This pull request was opened from and to a release candidate branch. This should only be done as part of the official Flutter release process. If you are attempting to make a regular contribution to the Flutter project, please close this PR and follow the instructions at Tree Hygiene for detailed instructions on contributing to Flutter.

Reviewers: Use caution before merging pull requests to release branches. Ensure the proper procedure has been followed.

gemini-code-assist

Code Review

This pull request introduces manual breakpoint continue handling for iOS 27+ devices in debug mode to prevent crashes caused by auto-continue failures. It adds a deviceVersion parameter to IOSCoreDeviceLauncher and LLDB, allowing LLDB to manually intercept stops, verify if they are caused by the JIT breakpoint, and resume execution. The changes are accompanied by corresponding test updates. Feedback on these changes suggests resolving a potential silent hang in the manual continue logic by resetting the stopped state upon resuming, correcting a misleading documentation comment for _targetStoppedPattern, and using Version.tryParse instead of Version.parse to robustly handle malformed SDK version strings.

gemini-code-assist · 2026-09-15T16:26:37Z

+            if (line.contains(_lldbProcessStopped)) {
+              processIsStoppedAfterAttaching = true;
+            }
+            if (processIsStoppedAfterAttaching) {
+              stopLogs.add(line);
+            }
+            if (line.contains(_targetStoppedPattern)) {
+              if (stopLogs.any((log) => log.contains('stop reason = breakpoint'))) {
+                await _lldbProcess?.stdinWriteln(_processContinueCommand);
+              } else {
+                stopLogs.forEach(printLine);
+                await _lldbProcess?.stdinWriteln(_threadBacktraceAllCommand);
+                await _lldbProcess?.stdinWriteln(_detachCommand);
+                processIsStoppedAfterAttaching = false;
+              }
+              return;
+            }
+            if (processIsStoppedAfterAttaching) {
+              if (line.contains(_lldbProcessResuming)) {
+                processIsStoppedAfterAttaching = false;
+                stopLogs.clear();
+              }
+              return;
            }


In the manual continue logic, if _processContinueCommand fails or if LLDB outputs any unexpected logs/errors before resuming, those logs will be captured in stopLogs and swallowed because processIsStoppedAfterAttaching remains true indefinitely. This can lead to silent hangs and make debugging extremely difficult.\n\nTo prevent this, we should set processIsStoppedAfterAttaching = false and clear stopLogs immediately when sending the continue command. We can then discard the resuming line (_lldbProcessResuming) by checking for it at the top of the manual continue block.

if (line.contains(_lldbProcessResuming)) {\n return;\n }\n\n if (line.contains(_lldbProcessStopped)) {\n processIsStoppedAfterAttaching = true;\n }\n if (processIsStoppedAfterAttaching) {\n stopLogs.add(line);\n }\n if (line.contains(_targetStoppedPattern)) {\n if (stopLogs.any((log) => log.contains('stop reason = breakpoint'))) {\n await _lldbProcess?.stdinWriteln(_processContinueCommand);\n processIsStoppedAfterAttaching = false;\n stopLogs.clear();\n } else {\n stopLogs.forEach(printLine);\n await _lldbProcess?.stdinWriteln(_threadBacktraceAllCommand);\n await _lldbProcess?.stdinWriteln(_detachCommand);\n processIsStoppedAfterAttaching = false;\n stopLogs.clear();\n }\n return;\n }\n if (processIsStoppedAfterAttaching) {\n return;\n }

gemini-code-assist · 2026-09-15T16:26:38Z

+  /// Pattern of lldb log when the application has started.
+  ///
+  /// Example: Target 0: (Flutter Gallery) stopped.
+  static final _targetStoppedPattern = RegExp(r'Target .* stopped.');


The documentation comment for _targetStoppedPattern is misleading. It states that the pattern is for when the application has started, but the pattern and example actually match when the application has stopped.

/// Pattern of lldb log when the application has stopped.\n ///\n /// Example: Target 0: (Flutter Gallery) stopped.\n static final _targetStoppedPattern = RegExp(r'Target .* stopped.');

gemini-code-assist · 2026-09-15T16:26:38Z

            fileSystem: globals.fs,
            processUtils: _processUtils,
            xcodeProjectInterpreter: globals.xcodeProjectInterpreter!,
+            deviceVersion: Version.parse(sdkVersionString),


Using Version.parse can throw a FormatException if sdkVersionString is malformed or not a valid semantic version. To make this more robust and follow defensive programming practices, use Version.tryParse instead, which safely returns null on parsing failures.

Suggested change

deviceVersion: Version.parse(sdkVersionString),

deviceVersion: Version.tryParse(sdkVersionString),

References

Defensive programming: ensure appropriate null/nil/None checks or other language-idiomatic guards exist before object property accesses. Ensure that invalid inputs or states are safely handled in all cases.

vashworth requested review from a team as code owners September 15, 2026 16:24

flutter-dashboard Bot added the CICD Run CI/CD label Sep 15, 2026

github-actions Bot added platform-ios iOS applications specifically tool Affects the "flutter" command-line tool. See also t: labels. labels Sep 15, 2026

github-actions Bot added platform-macos Building on or for macOS specifically a: desktop Running on desktop team-ios Owned by iOS platform team team-macos Owned by the macOS platform team labels Sep 15, 2026

vashworth requested a review from okorohelijah September 15, 2026 16:25

gemini-code-assist Bot reviewed Sep 15, 2026

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okorohelijah approved these changes Sep 15, 2026

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reidbaker approved these changes Sep 15, 2026

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reidbaker added the autosubmit Merge PR when tree becomes green via auto submit App label Sep 15, 2026

auto-submit Bot merged commit 8b9ed14 into flutter:flutter-3.48-candidate.0 Sep 15, 2026
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[CP-beta]On iOS 27+ devices, manually process lldb stops - #192814

[CP-beta]On iOS 27+ devices, manually process lldb stops#192814
auto-submit[bot] merged 1 commit into
flutter:flutter-3.48-candidate.0from
vashworth:cp_3.48_pr_191434

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	deviceVersion: Version.parse(sdkVersionString),
	deviceVersion: Version.tryParse(sdkVersionString),

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vashworth commented Sep 15, 2026

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