RFR 8067447: Factor out the shared implementation of the VM flags manipulation code

[David Holmes]

On 8/01/2015 1:59 AM, Jaroslav Bachorik wrote:
> On 7.1.2015 02:31, David Holmes wrote:
>> On 17/12/2014 8:19 PM, Jaroslav Bachorik wrote:
>>> Please, review the following change.
>>>
>>> Issue : https://bugs.openjdk.java.net/browse/JDK-8067447
>>> Webrev: http://cr.openjdk.java.net/~jbachorik/8067447/webrev.00
>>>
>>> This patch is a precursor for implementing
>>> https://bugs.openjdk.java.net/browse/JDK-8054890 which itself is a part
>>> of JEP-228 (https://bugs.openjdk.java.net/browse/JDK-8043764).
>>>
>>> Here, the code related to manipulating JVM flags is extracted to a
>>> separate ManagedFlags class and the codebease is adjusted to use this
>>> class.
>>
>> Not clear to me what this is addressing exactly - do we really need
>> platform specific variants of "set flag" ??
>
> It has just been moved from the corresponding attachListener_<os>.cpp
> files. And it is 'pd_set_flag' what, I suppose, means "platform dependent"?

Yes it does and it mostly made sense inside the already pd 
attachListener implementations, but it isn't obvious to me that it makes 
sense in the ManagedFlag context. It is the choice about whether the 
flag can be changed that is "pd" not the actual setting and those 
choices are inherent to the attachListener mechanism they are not 
inherent to ManagedFlags - so this refactoring seems wrong to me. What 
exactly is ManagedFlag supposed to represent?

>>
>> All the new code seems incorrect:
>>
>> jint ManagedFlags::pd_set_flag(const char* flag_name, const char*
>> flag_value, Flag::Flags origin, outputStream* out) {
>>     out->print_cr("flag '%s' cannot be changed", op->arg(0));
>>     return JNI_ERR;
>>   };
>>
>> op->arg(0) comes from the original code where op was an
>> AttachOperation*. Here is should be using flag_name.
>
> Correct. Slipped through and then replicated :/

And obviously never compiled. RFRs should be for tested code.

David
-----

> Updated webrev: http://cr.openjdk.java.net/~jbachorik/8067447/webrev.01
>
> -JB-
>
>>
>> David
>>
>>
>>> Thanks,
>>>
>>> -JB-
>