RFR: 8301403: Eliminate memory allocations in JVMFlag::printFlags during signal handling [v11]

[Gerard Ziemski]

On Fri, 26 Jul 2024 14:50:47 GMT, Gerard Ziemski <gziemski at openjdk.org> wrote:

>> Allocating memory while handling an error should be avoided, however `JVMFlag::printFlags()` is used by crash log and it allocates memory to print flags sorted (using qsort).
>> 
>> We avoid memory allocation by using BitMapView (using stack storage for array of indices) for markers in a simple O(n^2) algorithm that lets us print in alphabetical order. Performance was measured and it's not an issue.
>> 
>> Running MACH5 tests...
>
> Gerard Ziemski has updated the pull request incrementally with one additional commit since the last revision:
> 
>   need 32 bit version of LogBytesPerWord too

Thank you David, Thomas and Johan for all your feedback!

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PR Comment: https://git.openjdk.org/jdk/pull/20202#issuecomment-2258589999