RFR: 8222460: -XX:+PrintFlagsRanges prints incorrect range

[gerard ziemski]

On 4/15/19 12:58 AM, Per Liden wrote:
> When testing JDK-8222145 (Add -XX:SoftMaxHeapSize flag), I ran into 
> this issue.
>
> -XX:+PrintFlagsRanges prints incorrect value range for flags that are 
> associated with a constraint function. Instead of printing an empty 
> range "[ ...                           ]" is prints the default value 
> range for the type. It should do the opposite.
>
> The fix in jvmFlagRangeList.cpp is trivial. However, it has the side 
> effect that some options that were previously not tested are now 
> tested, and vice versa. As a result I had to exclude testing the max 
> range of two problematic options (ActiveProcessorCount and 
> G1PeriodicGCInterval). It might also be the cases that some of the 
> previously excluded options no longer need to be excluded, but I 
> didn't want to fiddle with that in this patch. If this is the case, I 
> suggest that is fixed in a follow up RFE.
>
> Testing: tier1-3 in all Oracle platforms, tier1-7 on Linux/x86_64
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8222460
> Webrev: http://cr.openjdk.java.net/~pliden/8222460/webrev.0
>
> /Per
>

hi Per,

I'm sorry that this caused an issue for you.

I think the original idea here was that for those flags with a 
constraint, we wanted to show the possible range, from which the 
constraint will further restrict the final value. However, that is 
tricky to test without exposing the constraint function, as evidenced by 
the exclusion list in the test.

For those flags without range and constraint, the implicit range is the 
max range of the flag's type, so the idea here was that such flag was 
"untestable" for practical purposes, so we print an empty range.

I believe that a better fix here might be to print an empty range in 
both cases.

The cleanup of the exclusion flags in the test (and removal of default 
print range functions, if not needed anymore) can be handled by a 
followup issue.


cheers