RFR: 8371637: allocateNativeInternal sometimes return incorrectly aligned memory [v2]

[Harald Eilertsen]

On Fri, 14 Nov 2025 10:19:09 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> Harald Eilertsen has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Second try to fix alignment for native segments
>>    
>>    Introducing a helper function as suggested by JornVernee to decide on
>>    the proper alignment based on the segment size.
>>    
>>    This work was sponsored by: The FreeBSD Foundation
>>    
>>    Co-authored-by: JornVernee
>>  - Test that native segments don't overlap
>>    
>>    This work was sponsored by: The FreeBSD Foundation
>
> The fix is simple and pragmatic. The main difference between this and what I described is that by singling out FreeBSD, we won't be able to support cases where e.g. a developer runs on Linux, but using LD_PRELOAD to use a different allocator like jemalloc? It's a cornery case, but one I've seen from time to time to take advantage of some of the "hardening" features provided by jemalloc (and diagnose memory issues). Of course, we can also keep this PR as is, and then address other (more cornery cases) in separate PRs.

@mcimadamore That's a very good point! I'll try to update the patch, and see how it works out.

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PR Comment: https://git.openjdk.org/jdk/pull/28235#issuecomment-3532137468