RFR: 8256450: Add gz option to jmap to write a gzipped heap dump [v2]

[Chris Plummer]

On Wed, 18 Nov 2020 10:37:43 GMT, Lin Zang <lzang at openjdk.org> wrote:

>> So I assume then that the `op->arg(2)` reference will return `NULL` when an older `jmap` is used? Is that correct?
>
> Hi @plummercj,
>      For old jmap, if "gz" option is used in commandline, it prompt usage info indicating that option is illegal.
>      if "gz" option is not used, the op->arg(2) will be an empty string "", which is set from the attacher side in the method execute() of VirtualMachineImpl.java.

Ok, I see now that 3 args are always written, even if empty, so you at least get a "" if there is no value for the argument position.

-------------

PR: https://git.openjdk.java.net/jdk/pull/1251