RFR(trivial): 8232768: Configuration with --disable-cds --enable-generate-classlist should be reported as an error

[Magnus Ihse Bursie]

On 2019-10-22 14:52, Jie Fu wrote:
> Hi Magnus,
>
> Thanks for your review and valuable comments.
> It is the second case since the VM will report an error for 
> DumpLoadedClassList when CDS is disabled.
> So generate-classlist *never* will work with CDS disabled.
>
> Updated: http://cr.openjdk.java.net/~jiefu/8232768/webrev.01/
This looks good to me. Do you need a sponsor for the patch?

/Magnus
>
> Please review it and give me some advice.
>
> Thanks a lot.
> Best regards,
> Jie
>
> On 2019/10/22 下午5:54, Magnus Ihse Bursie wrote:
>> On 2019-10-22 09:44, Jie Fu wrote:
>>> Hi all,
>>>
>>> May I get reviews for this one-line change?
>>>
>>> JBS:    https://bugs.openjdk.java.net/browse/JDK-8232768
>>> Webrev: http://cr.openjdk.java.net/~jiefu/8232768/webrev.00/
>>>
>>> This kind of configuration, with both --disable-cds and 
>>> --enable-generate-classlist, will fail.
>>> The failure is caused by -XX:DumpLoadedClassList [1], which doesn't 
>>> work as expected when cds is disabled.
>>>
>>> It might be better to produce an error.
>> I'm not sure I agree with this fix. Checking the code, we make an 
>> effort to determine if we should warn the user:
>>
>>   # Check if it's likely that it's possible to generate the 
>> classlist. Depending
>>   # on exact jvm configuration it could be possible anyway.
>>   if test "x$ENABLE_CDS" = "xtrue" && 
>> (HOTSPOT_CHECK_JVM_VARIANT(server) || 
>> HOTSPOT_CHECK_JVM_VARIANT(client) || HOTSPOT_CHECK_JVM_FEATURE(cds)); 
>> then
>>
>> Only if the user *explicitly* sets --enable-generate-classlist, the 
>> warning is printed. The comment clearly states that this might be 
>> possible anyway, given the circumstances, so I believe a warning, and 
>> not an error, is the right thing here. The user explicitly requests 
>> generate-classlist. We warn that it might not work, but we allow it 
>> since it can work in cases we don't really know about.
>>
>> If it is the case that generate-classlist *never* will work with CDS 
>> disabled (this sounds reasonable, but I don't know if this really is 
>> the case), and you want to catch this, then I suggest you restructure 
>> the code so you catch the CDS && generate-classlist case separately, 
>> and give a fatal error for that, and then keep the current check for 
>> jvm variants/features and let it keep producing a warning for that.
>>
>> /Magnus
>>>
>>> Thanks a lot.
>>> Best regards,
>>> Jie
>>>
>>> [1] 
>>> http://hg.openjdk.java.net/jdk/jdk/file/ca620b06b5c9/make/GenerateLinkOptData.gmk#l68
>>>
>>>
>>
>