RFR: 8257234 : Add gz option to SA jmap to write a gzipped heap dump [v14]

[Lin Zang]

On Thu, 4 Feb 2021 03:54:26 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

>> Lin Zang has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - fix an issue of double printing error message.
>>  - fix jcmd jmap issue and add test in BascJMapTest and code refine
>
>> > I have found that there is a bug in jcmd jmap, it could accept the argument "gz=" with no value specified.
>> > so jmap -dump:file=a.hprof,gz= could generate dump file successfully.
>> 
>> After re-think of it, the jcmd jmap issue mentioned here seems not quite related with this PR, so maybe a standalone one is better? What do you think?
> 
> That's probably a good idea since this PR is for SA changes, and it's probably best not to mix it with attach api changes.

Dear @plummercj and @sspitsyn, 
I have uploaded a new change that fix some issues in argument parsing and segment dump. Also added the sub-test in HeapDumpTest.java. 
Would you like to help review again?
Thanks a lot for your patience and suggestion!

-Lin

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PR: https://git.openjdk.java.net/jdk/pull/1712