RFR: 8319875: Add macOS implementation for jcmd System.map [v17]

[Simon Tooke]

On Thu, 12 Dec 2024 19:46:37 GMT, Sonia Zaldana Calles <szaldana at openjdk.org> wrote:

>> Simon Tooke has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 35 commits:
>> 
>>  - Merge branch 'openjdk:master' into pr_macos_system_dump
>>  - fix crash due to uninitilized pointer
>>  - whitespace error
>>  - changes from revue
>>  - add constant
>>  - fix whitespace
>>  - combine like 128MB regions
>>  - fix trailing whitesdpae errors
>>  - latest cleanup, get rid of dll info
>>  - change format strings to display all digits properly
>>  - ... and 25 more: https://git.openjdk.org/jdk/compare/a6277bb5...c5cb0f97
>
> src/hotspot/os/bsd/memMapPrinter_macosx.cpp line 352:
> 
>> 350:       break;
>> 351:     }
>> 352:     ::bzero(&region_info_with_path, sizeof(region_info_with_path));
> 
> Should we use memset instead?

A very good question!  Changing it now would invalidate the reviews, unfortunately.  Portability is not a concern here as it's for macOS only.  Since bzero only ever zeros memory, it _can_ be slightly faster: [one discussion](https://fdiv.net/2009/01/14/memset-vs-bzero-ultimate-showdown).

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PR Review Comment: https://git.openjdk.org/jdk/pull/20953#discussion_r1884184636