RFR: 8257234 : Add gz option to SA jmap to write a gzipped heap dump [v9]

[Lin Zang]

On Wed, 27 Jan 2021 20:22:00 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

>>> Do you think it is reasonable to treat "gz=[number]/[non-number]" differently in this case? or should it just exit with error for all "gz=" options that is not in the range of compression level? BTW, I think your suggested code is better if we consider all illegal compression level as an error.
>> 
>> I think we should produce an error for something like `gz=abc` rather than use that as the filename, because I think it is likely user error. However, then you also need to figure out what to do with `gz=1 gz=abc`. Since the first argument is a proper `gz=` argument, you might miss the fact that the second also starts with `gz=` and accept it as a filename. Maybe in this example that is ok, but what if the user specifies `gz=1 gz=2`. Now it would seem they accidentally did two `gz=` arguments and an error should be produced, so I would suggest just always producing an error if the filename starts with `gz=`.
>
>> I think we should produce an error for something like gz=abc rather than use that as the filename, because I think it is likely user error.
> Agreed. My suggestion was exactly this. We have to return an error in any attempt to start filename with "gz=". It will also simplify the code and make it more straightforward.

@sspitsyn @plummercj, Thanks for your suggestion, I have made a fix of filename logic.

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