fix(macos): Guard nil WKWebView title to prevent native SIGSEGV by ajpinedam · Pull Request #23642 · unoplatform/uno · GitHub
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fix(macos): Guard nil WKWebView title to prevent native SIGSEGV#23642

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fix(macos): Guard nil WKWebView title to prevent native SIGSEGV#23642
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@ajpinedam

@ajpinedam ajpinedam commented Jul 3, 2026 •
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GitHub Issue: #23641

PR Type:

🐞 Bugfix

What changed? 🚀

uno_webview_get_title (macOS Skia native WebView) called strdup(webview.title.UTF8String) directly. WKWebView.title is nullable; when it is nil, [nil UTF8String] returns NULL and strdup(NULL) dereferences null → SIGSEGV. This guards it:

NSString *title = webview.title ?: @"";
return strdup(title.UTF8String);

"" preserves the existing behavior: CoreWebView2.DocumentTitle already coalesces to "", _previousTitle seeds to "" (so no spurious DocumentTitleChanged), and it matches WinUI parity (a title-less page returns ""). Allocation/free ownership is unchanged (still a strdup buffer freed by the UTF-8 return marshaller).

Also adds a When_DocumentTitle_Before_Navigation runtime test asserting DocumentTitle returns "" (rather than crashing) on a fresh web view.

Scope / honesty note: this targets the intermittent macOS 26 / x64 SIGSEGV in the Given_WebView2.When_ExecuteScriptAsync* runtime tests (#23641). The crash could not be reproduced locally (~65 runs on a matching macOS 26.4.1 / x64 machine, incl. NSZombieEnabled and MallocScribble; instrumentation showed title was never nil across ~70 navigations). So this is a defensive nullability fix, not a confirmed root-cause fix — but WKWebView.title is nullable by API, so strdup(NULL) is a real latent crash worth closing regardless. Whether it resolves the CI crash will be shown by the macOS runtime-test leg; #23641 is left open until confirmed.

PR Checklist ✅

  • 🧪 Added a runtime test (When_DocumentTitle_Before_Navigation)
  • 📚 Docs — N/A (internal native fix, no public API change)
  • 🖼️ Validated PR Screenshots Compare Test Run results — N/A (no visual change)
  • ❗ Contains NO breaking changes
  • 👀 Reviewed 2 other open pull requests

🤖 Generated with Claude Code

https://claude.ai/code/session_0178mJtoQEwreA2zrADWUgqP

Copilot AI review requested due to automatic review settings July 3, 2026 19:23
@github-actions github-actions Bot added platform/macos 🍏 Categorizes an issue or PR as relevant to the macOS platform area/automation Categorizes an issue or PR as relevant to project automation labels Jul 3, 2026
Copilot AI reviewed Jul 3, 2026
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Pull request overview

Defensive hardening for the macOS Skia native WebView title accessor to avoid a native crash when WKWebView.title is nil, plus a runtime test covering the “title before navigation” case.

Changes:

  • Guard WKWebView.title against nil in uno_webview_get_title before calling strdup.
  • Add a runtime test asserting CoreWebView2.DocumentTitle returns "" on a fresh WebView2 (no navigation yet).
  • Add a new SamplesApp manual test page for ContentDialog auto-focus / soft-keyboard behavior (appears unrelated to this PR’s stated scope).

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File Description
src/Uno.UI.Runtime.Skia.MacOS/UnoNativeMac/UnoNativeMac/UNOWebView.m Prevents strdup(NULL) by coalescing nullable WKWebView.title to an empty string.
src/Uno.UI.RuntimeTests/Tests/Microsoft_UI_Xaml_Controls/Given_WebView2.cs Adds regression coverage for reading DocumentTitle before any navigation.
src/SamplesApp/SamplesApp.Samples/Windows_UI_Xaml/FocusManager/ContentDialog_AutoFocusTextBox.xaml.cs Adds a new manual sample page (also contains a build-breaking unused using).
src/SamplesApp/SamplesApp.Samples/Windows_UI_Xaml/FocusManager/ContentDialog_AutoFocusTextBox.xaml XAML UI for the new manual sample page.

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Comment thread ...esApp/SamplesApp.Samples/Windows_UI_Xaml/FocusManager/ContentDialog_AutoFocusTextBox.xaml.cs Outdated
Comment thread ...esApp/SamplesApp.Samples/Windows_UI_Xaml/FocusManager/ContentDialog_AutoFocusTextBox.xaml.cs Outdated
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unodevops commented Jul 3, 2026

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🤖 Your WebAssembly Skia Sample App stage site is ready! Visit it here: https://unowasmprstaging.z20.web.core.windows.net/pr-23642/wasm-skia-net9/index.html

Copilot AI review requested due to automatic review settings July 3, 2026 22:51
Copilot AI reviewed Jul 3, 2026
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Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

Comment thread src/Uno.UI.RuntimeTests/Tests/Microsoft_UI_Xaml_Controls/Given_WebView2.cs
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unodevops commented Jul 3, 2026

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🤖 Your WebAssembly Skia Sample App stage site is ready! Visit it here: https://unowasmprstaging.z20.web.core.windows.net/pr-23642/wasm-skia-net9/index.html

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unodevops commented Jul 4, 2026

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⚠️⚠️ The build 220694 has failed on Uno.UI - CI.

Copilot AI review requested due to automatic review settings July 4, 2026 05:30
Copilot AI reviewed Jul 4, 2026
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Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

Comment thread src/Uno.UI.RuntimeTests/Tests/Microsoft_UI_Xaml_Controls/Given_WebView2.cs
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unodevops commented Jul 4, 2026

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🤖 Your WebAssembly Skia Sample App stage site is ready! Visit it here: https://unowasmprstaging.z20.web.core.windows.net/pr-23642/wasm-skia-net9/index.html

ajpinedam and others added 3 commits July 4, 2026 18:38
@ajpinedam
fix(macos): Guard nil WKWebView title
31398ed
@ajpinedam
chore: accept pr suggestion
da4bb8c 
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
@ajpinedam
fix: Restore signature in When_DocumentTitle test
ea15d2a
Copilot AI review requested due to automatic review settings July 4, 2026 22:41
@ajpinedam ajpinedam force-pushed the dev/anpi/investigate.crash.macos26.x64 branch from 7bb0e11 to ea15d2a Compare July 4, 2026 22:41
Copilot AI reviewed Jul 4, 2026
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Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

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unodevops commented Jul 4, 2026

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area/automation Categorizes an issue or PR as relevant to project automation platform/macos 🍏 Categorizes an issue or PR as relevant to the macOS platform

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