RFR: 8287007: [cgroups] Consistently use stringStream throughout parsing code [v3]

[Severin Gehwolf]

On Wed, 8 Jun 2022 12:09:27 GMT, Severin Gehwolf <sgehwolf at openjdk.org> wrote:

>> Please review this cleanup change in the cgroup subsystem which used to use hard-coded stack allocated
>> buffers for concatenating strings in memory. We can use `stringStream` instead which doesn't have the issue
>> of hard-coding maximum lengths (and related checks) and makes the code, thus, easier to read.
>> 
>> While at it, I've written basic `gtests` verifying current behaviour (and the same for the JDK code). From
>> a functionality point of view this is a no-op (modulo the one bug in the substring case which seems to be
>> there since day one). I'd prefer if we could defer any change in functionality to a separate bug as this is
>> meant to only use stringStream throughout the cgroups code.
>> 
>> Testing:
>> - [x] Container tests on Linux x86_64 cgroups v1 and cgroups v2
>> - [x] Added tests, which I've verified also pass before the stringStream change
>> 
>> Thoughts?
>
> Severin Gehwolf has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove fix for substring match

@erikj79 Do you know why the SKARA bots didn't move this to `ready` by now? Is there an issue with the bots? Thanks!

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PR: https://git.openjdk.org/jdk/pull/8969