RFR: 8351733: [macos] Crash when creating too many nested event loops [v2]

[Andy Goryachev]

On Sat, 22 Mar 2025 18:05:13 GMT, Martin Fox <mfox at openjdk.org> wrote:

>> modules/javafx.graphics/src/main/native-glass/mac/GlassApplication.m line 759:
>> 
>>> 757: + (BOOL)canStartNestedEventLoop
>>> 758: {
>>> 759:     return nestedRunLoopRunCount <= 250;
>> 
>> would it be possible to determine the source of this limit - a header perhaps?
>> could it be dependent on os version?
>
> I have not been able to find any header detailing this limit. My guess is that someone at Apple decided to add an internal check for infinite recursion to ensure the app fails early with a clear message and decided 255 levels of nesting should be enough for anyone. The crash log contains these lines (which also show up in the debugger):
> 
>> Application Specific Information:
>> Too many nested CFRunLoopRuns
> 
> The check is new with macOS 15. I tested some standalone code on macOS 13 and 14 and had no problem reaching a nesting level of 500. But I don't think we should make the JavaFX check conditional on OS version number; I wouldn't want a JavaFX app that worked on macOS 14 to fail mysteriously on macOS 15.

I second Kevin's suggestion to add a constant with a good comment, since it's an arbitrarily chosen limit.  It would explain the "why" if/when the things change in macOS.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1741#discussion_r2010372776