RFR: 8366062: [ubsan] add non-zero offset to nullptr in cds/archiveBuilder.cpp [v6]

[David Holmes]

On Wed, 17 Sep 2025 09:53:28 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 incrementally with one additional commit since the last revision:
> 
>   fix after wrong merge.

BTW as per your related PR there could be some debate about the type used for the cast that then leads to questions about the types used by the other variables in the calculations. I decided not to open that can-of-worms here, but if a decision is made in that other PR then you may want to apply the same here.

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PR Comment: https://git.openjdk.org/jdk/pull/26983#issuecomment-3305129639