Make +UseZGC fail hard when it is unsupported

Per Liden per.liden at
Thu Jun 14 15:58:23 UTC 2018

Hi Aleksey,

On 06/14/2018 10:59 AM, Aleksey Shipilev wrote:
> On 06/14/2018 10:55 AM, Per Liden wrote:
>> On 06/14/2018 10:45 AM, Aleksey Shipilev wrote:
>>> I have build recent workspace, and forgot to enable zgc in configure. Yet, the runs proceeded as
>>> usual, and G1 was automatically selected. Per, can you make this failure fatal?
>> This behavior is in line with how this mechanism works for all other GCs, so it's not ZGC specific.
>> E.g. if you build a minimal VM you should see the same behavior if you try to enable, say G1.
>> However, it can certainly be debated whether this is a good behavior or not, and I tend to agree
>> with you that it's not.
> Sure. My point was that users would become exposed to this with optionally-compiled experimental GC
> very often now. Hardly anyone uses minimal VM, but everyone would use server VM with optional GCs.
> Would be sad to see reports against ZGC, Shenandoah, Epsilon that are not actually running those GCs.
> Since you were redoing the gcConfig machinery, would you have cycles to make RFE that makes this
> warning fatal?

Sure, I'll look into it.


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