RFR: 8310228: Improve error reporting for uncaught native exceptions on Windows

[Jorn Vernee]

On Fri, 16 Jun 2023 16:00:03 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

> Prevents a stack overflow (or other fatal error) from occurring when handling an unknown exception. See JBS issue for full problem outline.
> 
> WRT implementation:
> - I've refactored `Handle_FLT_Exception` to check the exception code on 64 bit Windows as well. It now returns a boolean indicating whether the exception was recognized and handled. 
> - For x86, I've created a new Uncaugh_Exception_Handler function which implements the uncaught exception handler. This new function replaces the previous use of `Handle_FLT_Exception` as uncaught exception handler. x86 also supports exception chaining through a previous exception handler stored in `prev_uef_handler`. But, on 64 bit windows this field is never set, so we don't need to try to execute the fallback handler on 64 bit. Hence, it seemed clearer to factor out that bit to a separate function. Both the x86 and 64 bit impls call the `handle_FLT_exception` function.
> 
> I've tested this patch locally on Windows x64, I will need some help testing this on Windows x86.
> 
> Testing: tier 1-4

src/hotspot/os/windows/os_windows.cpp line 2526:

> 2524:       return true;
> 2525:     }
> 2526: #endif // !_WIN64

The diff looks a bit mixed up, but I've essentially just moved this _WIN64 code into the switch which checks the exception code, so that we only try to restore MXCSR when we see a FLT* exception.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14523#discussion_r1236920072