RFR: JDK-8318636: Add jcmd to print annotated process memory map [v3]

[Thomas Stuefe]

On Fri, 27 Oct 2023 08:38:02 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

>> Thomas Stuefe has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains four commits:
>> 
>>  - Merge master and solve merge conflicts
>>  - small fixes
>>  - start from VM op; show more thread details
>>  - start
>
> src/hotspot/os/linux/memMapPrinter_linux.cpp line 39:
> 
>> 37:   char dev[20 + 1];
>> 38:   char inode[20 + 1];
>> 39:   char filename[1024 + 1];
> 
> Maybe use `PATH_MAX` here? Potentially +1 to account for null byte.

That is surprisingly tricky since there is no way to specify variable sizes with scanf, unlike printf. 

One could rely on PATH_MAX being a pure numerical ("4096") and assemble the format string with preprocessor magic, but that falls apart if PATH_MAX is e.g. a constant. 

One could build up the format string dynamically at runtime, but that will trigger warnings in code linters and possibly when building since the format string is supposed to be a literal.

Also, the PATH_MAX size is pretty arbitrary. Paths can get infinitely long with nested links. So there is no safe limit anyway. May just as well keep 1024 then, since that should be enough for 99% of cases.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16301#discussion_r1374420720