Fix: Add _DISABLE_CONSTEXPR_MUTEX_CONSTRUCTOR to prevent crashes

[EllieTellie]

Description

Fixes crash when running on systems with older Visual C++ runtimes.
MSVC broke ABI compatibility with the release of MSVC 17.10
We can define _DISABLE_CONSTEXPR_MUTEX_CONSTRUCTOR to CMakeLists.txt to fix this and make Firebase compatible with older runtimes on Windows.

Testing

Tested C#/Unity application with FirebaseCppApp-12_10_0.dll built from source with this additional fix.
Copied msvcp140.dll, vcruntime140.dll and vcruntime140_1.dll from a older runtime (2019 v16.11) to the root folder (where the .exe lives).
Verified it crashes the application without the fix.
Verified it does not crash the application with the fix.
If required I could provide a repro project if desired, but it will have to contain these msvc dlls.

---

Type of Change

Place an x the applicable box:

• Bug fix. Add the issue # below if applicable.
• New feature. A non-breaking change which adds functionality.
• Other, such as a build process or documentation change.

---

Fixes: firebase/firebase-unity-sdk#1291

References

• Microsoft STL Issue: VCRuntime incompatibility with older version in mutex code microsoft/STL#4730
• Firebase Unity Issue: [Bug] Unity App Crash on launch with Firebase 12.10.0 firebase-unity-sdk#1291

Notes

• Bug fixes and feature changes require an update to the Release Notes section of release_build_files/readme.md.
• Read the contribution guidelines CONTRIBUTING.md.
• Changes to the public API require an internal API review. If you'd like to help us make Firebase APIs better, please propose your change in a feature request so that we can discuss it together.

[gemini-code-assist]

Summary of Changes

Hello @EllieTellie, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request provides a crucial fix for a crash experienced by Firebase applications on Windows systems running older Visual C++ runtimes. By introducing a specific compiler definition in the CMake build configuration, it effectively mitigates an ABI incompatibility issue that arose with a recent MSVC update, thereby enhancing the robustness and backward compatibility of Firebase.

Highlights

• Crash Fix: Addresses a crash occurring on systems utilizing older Visual C++ runtimes.
• ABI Compatibility: Resolves an ABI incompatibility issue introduced by MSVC 17.10.
• Compiler Definition: Implements the fix by adding the _DISABLE_CONSTEXPR_MUTEX_CONSTRUCTOR definition to CMakeLists.txt.
• Broader Compatibility: Ensures Firebase applications maintain compatibility with older Windows runtimes.

🧠 New Feature in Public Preview: You can now enable Memory to help Gemini Code Assist learn from your team's feedback. This makes future code reviews more consistent and personalized to your project's style. Click here to enable Memory in your admin console.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	/gemini review	Performs a code review for the current pull request in its current state.
Pull Request Summary	/gemini summary	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	/gemini help	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Footnotes

1. Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

[gemini-code-assist]

Code Review

This pull request addresses a critical crash on Windows systems with older Visual C++ runtimes by defining _DISABLE_CONSTEXPR_MUTEX_CONSTRUCTOR. The change is correct and well-placed within the MSVC-specific configuration in CMakeLists.txt. I have one suggestion to improve the maintainability of this workaround by adding a reference to the upstream issue in the code comment.

[a-maurice]

Thanks for putting this together, I will run our tests to make sure this won't have any other side effects.

[EllieTellie]

Thanks for putting this together, I will run our tests to make sure this won't have any other side effects.

No problem, I saw tests had passed and thought to rebase it to main but that now requires tests to run again. I'll just leave it alone next time.

[a-maurice]

Thanks for putting this together, I will run our tests to make sure this won't have any other side effects.

No problem, I saw tests had passed and thought to rebase it to main but that now requires tests to run again. I'll just leave it alone next time.

No worries, it's sorta a hassle. We have a scheduled release next week, so this and your other change should be rolled into that. Thanks for sending these in.