This is where the crash happens

Oct 13, 2025 by wbrum.org 88 views

Introduction

The SDL (Simple DirectMedia Layer) library is a popular, cross-platform development library used for creating games and other interactive applications. However, like any other complex software, it is not immune to bugs and issues. In this article, we will discuss a specific problem that has been reported in the SDL3 3.2.8 version, where creating child windows on macOS crashes the application.

The Issue

The issue is caused by the SetupWindowData method in the Cocoa backend of SDL3, which is responsible for setting up the window data for a newly created window. When a child window is created using the addChildWindow: method, it indirectly accesses the window's internal data before it is even stored into the window further down the SetupWindowData method. This leads to a crash in the SDL_SetWindowSafeAreaInsets method.

The Crash Path

To understand the crash path, let's follow the sequence of events that lead to the crash:

[NSWindow addChildWindow:nswindow ordered:NSWindowAbove];: This method is called to add a child window to the parent window.
[SDL3Cocoa_WindowListener observeValueForKeyPath... ]: This method is called to observe the changes in the window's properties.
SDL_SendWindowEvent: This method is called to send a window event to the SDL library.
SDL_OnWindowShown: This method is called when the window is shown.
ApplyWindowFlags: This method is called to apply the window flags.
SDL_SetWindowFullscreen_REAL: This method is called to set the window to full screen.
SDL_UpdateFullscreenMode: This method is called to update the full screen mode.
Cocoa_SetWindowFullscreen: This method is called to set the window to full screen using the Cocoa backend.
SDL_SetWindowSafeAreaInsets: This method is called to set the safe area insets for the window. This is where the crash happens.

The `FIXME` Comment

There is a FIXME comment directly below the addChildWindow: method, which suggests that there might be a related issue. However, it is not clear what this issue is or how it is related to the crash.

Conclusion

In conclusion, the crash in creating child windows on macOS in SDL3 3.2.8 is caused by the indirect access to the window's internal data in the SetupWindowData method. The crash path is complex and involves multiple methods in the SDL library. To fix this issue, the SDL team needs to investigate the crash path and identify the root cause of the problem. This might involve modifying the SetupWindowData method to ensure that the window's internal data is properly stored before it is accessed.

Recommendations

To avoid this issue, developers using SDL3 3.2.8 on macOS should avoid creating child windows until the issue is fixed. In the meantime, they can try to work around the issue by using a different method to create child windows or by modifying the SDL library to fix the crash.

Future Work

The SDL team should prioritize fixing this issue in the next version of the library. This will ensure that developers can create child windows on macOS without encountering the crash. Additionally, the team should investigate the FIXME comment and determine if it is related to the crash.

Q: What is the issue with creating child windows on macOS in SDL3 3.2.8?

A: The issue is caused by the indirect access to the window's internal data in the SetupWindowData method. When a child window is created using the addChildWindow: method, it indirectly accesses the window's internal data before it is even stored into the window further down the SetupWindowData method. This leads to a crash in the SDL_SetWindowSafeAreaInsets method.

Q: What is the crash path that leads to the issue?

A: The crash path is as follows:

[NSWindow addChildWindow:nswindow ordered:NSWindowAbove];
[SDL3Cocoa_WindowListener observeValueForKeyPath... ]
SDL_SendWindowEvent
SDL_OnWindowShown
ApplyWindowFlags
SDL_SetWindowFullscreen_REAL
SDL_UpdateFullscreenMode
Cocoa_SetWindowFullscreen
SDL_SetWindowSafeAreaInsets (This is where the crash happens)

Q: Is the `FIXME` comment related to the issue?

A: It is not clear what the FIXME comment is related to, but it is directly below the addChildWindow: method. It is possible that the FIXME comment is related to the issue, but further investigation is needed to determine the exact relationship.

Q: How can developers avoid this issue?

A: Developers can avoid this issue by:

Avoiding creating child windows on macOS until the issue is fixed
Working around the issue by using a different method to create child windows
Modifying the SDL library to fix the crash

Q: What should the SDL team do to fix this issue?

A: The SDL team should:

Investigate the crash path and identify the root cause of the problem
Modify the SetupWindowData method to ensure that the window's internal data is properly stored before it is accessed
Prioritize fixing this issue in the next version of the library

Q: When can we expect a fix for this issue?

A: The SDL team has not provided a specific timeline for fixing this issue. However, it is recommended to follow the SDL development mailing list and bug tracker for updates on the issue.

Q: Can I help with fixing this issue?

A: Yes, if you are a developer with experience in the SDL library, you can help by:

Reporting the issue on the SDL bug tracker
Providing a patch or fix for the issue
Contributing to the SDL development process

In conclusion, the crash in creating child windows on macOS in SDL3 3.2.8 is a complex issue that requires further investigation. The SDL team needs to identify the root cause of the problem and modify the SetupWindowData method to ensure that the window's internal data is properly stored before it is accessed. Until then, developers should avoid creating child windows on macOS or work around the issue by modifying the SDL library.