RFR: 8366062: [ubsan] add non-zero offset to nullptr in cds/archiveBuilder.cpp [v5]

[David Holmes]

On Tue, 16 Sep 2025 09:36:22 GMT, Afshin Zafari <azafari at openjdk.org> wrote:

>> It is acceptable that the `SharedBaseAddress` option gets `0` at command line. The corresponding pointer arithmetic with `0` (`nullptr`) in archiveBuilder is UB.
>> Specific casts are used to avoid UBSAN error.
>> 
>> Tests:
>> linux-x64-debug: tier1 passed
>
> Afshin Zafari has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains five commits:
> 
>  - Merge remote-tracking branch 'origin/master' into _8366062_ubsan_nullptr_plus_nz_offset
>  - comment fixed
>  - Merge remote-tracking branch 'origin/master' into _8366062_ubsan_nullptr_plus_nz_offset
>  - comments improved
>  - 8366062: [ubsan] add non-zero offset to nullptr in cds/archiveBuilder.cpp

@afshin-zafari  it looks like you have mis-merged this and have kept the old MetaspaceShared names instead of the new AOTMetaspace ones.

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Changes requested by dholmes (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/26983#pullrequestreview-3232165840