RFR: 8351334: [ubsan] memoryReserver.cpp:552:60: runtime error: applying non-zero offset 1073741824 to null pointer [v4]

[Axel Boldt-Christmas]

On Mon, 15 Sep 2025 08:49:42 GMT, Afshin Zafari <azafari at openjdk.org> wrote:

>> The minimum acceptable value was 0 where using it as address was problematic according to UBSAN.
>> The acceptable value is changed to 64K.
>> 
>> Tests:
>> linux-x64 tier1
>
> Afshin Zafari has updated the pull request incrementally with one additional commit since the last revision:
> 
>   fixes

I agree with @jdksjolen that I think we should go towards using `uintptr_t` as far as possible. Maybe we do it piecemeal like this. Eventually we could end up using `uintptr_t` until we reach the os layer. 

Looks like you at least have to clean up the `uintptr_t` vs `uint64_t` in the touched methods as some platforms have them define as `unsigned long` vs `unsigned long long`.

src/hotspot/share/memory/memoryReserver.cpp line 612:

> 610:       }
> 611:       lowest_start = align_up(lowest_start, attach_point_alignment);
> 612:       assert(lowest_start < highest_start, "lowest: " INTPTR_FORMAT " highest: " INTPTR_FORMAT,

We should support a start which is a single value.
Suggestion:

      assert(lowest_start <= highest_start, "lowest: " INTPTR_FORMAT " highest: " INTPTR_FORMAT,

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PR Review: https://git.openjdk.org/jdk/pull/26955#pullrequestreview-3223852121
PR Review Comment: https://git.openjdk.org/jdk/pull/26955#discussion_r2348500738