RFR: 8367485: os::physical_memory is broken in 32-bit JVMs when running on 64-bit OSes [v5]

[Thomas Stuefe]

On Thu, 18 Sep 2025 14:35:49 GMT, Anton Artemov <duke at openjdk.org> wrote:

>> Hi, please consider the following changes:
>> 
>> In this PR we address the overflow issue in `os::physical_memory()` on Linux, which can occur when running a 32-bit JVM on a 64-bit machine, introduced by https://bugs.openjdk.org/browse/JDK-8357086. The problem is that the product of _SC_PHYS_PAGES and _SC_PAGESIZE can overflow according to the documentation. 
>> 
>> The issue is addressed by changing the output type of all related functions to `uint64_t`.
>> 
>> Tested in tiers 1 - 5.
>
> Anton Artemov has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - 8367485: Indentation fix.
>  - 8367485: Addressed reviewer's comments.

Ironically, the 32-bit build now fails. (tested with arm32).

Watch out for places where the newly typed vars are fed into `%zu`. Example below.

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Changes requested by stuefe (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/27335#pullrequestreview-3240141260