RFR 8014431 : cleanup warnings indicated by the -Wunused-value compiler option on linux

[Calvin Cheung]

I've updated the webrev. It's at the same location:
     http://cr.openjdk.java.net/~ccheung/8014431/webrev/

thanks,
Calvin

On 5/23/2013 10:55 AM, Calvin Cheung wrote:
> On 5/23/2013 5:45 AM, David Holmes wrote:
>> Hi Calvin,
>>
>> Mostly looks okay to me. A few comments
> Thanks for your review.
>>
>> src/share/vm/memory/universe.cpp
>>
>> Seems like a real bug!
>>
>> -- 
>>
>> src/share/vm/opto/memnode.cpp:
>>
>> I think it is cleaner to add the (void) to the macro definition as in 
>> other cases:
>> #define verify_memory_slice(m,i,n) (void)(0) // PRODUCT version is no-op
>>
> I've fixed it.
>> ---
>>
>> src/share/vm/runtime/perfData.hpp
>>
>> This can't be right:
>>
>> 773 return create_string_variable(ns, name, (int)0, s, CHECK_NULL);
>>
>> why do we have to cast 0 to int ????
> I've removed it.
>>
>> ---
>>
>> src/share/vm/services/diagnosticArgument.cpp
>>
>> Another real bug!
>>
>> ---
>>
>> src/share/vm/utilities/taskqueue.hpp
>>
>> I do not understand this code:
>>
>> ! // g++ complains if the volatile result of the assignment is unused.
>> ! const_cast<E&>(_elems[localBot] = t);
>>
>> why do we even need the const cast? How is the assignment not used ???
> I've tried without the const cast and got the following error:
> /scratch/cccheung/hs25/src/share/vm/utilities/taskqueue.hpp:348: 
> error: object of type ‘volatile StarTask&’ will not be accessed in 
> statement
>
> There was an original comment about the const cast as follows:
> 343 // g++ complains if the volatile result of the assignment is unused.
> 344 const_cast<E&>(_elems[localBot] = t);
>
> thanks,
> Calvin
>>
>> I understand your fix of adding (void) but I'm baffled by the 
>> original code.
>>
>> ---
>>
>> Thanks,
>> David
>> -----
>>
>> On 22/05/2013 5:32 AM, Calvin Cheung wrote:
>>> This change is for fixing the errors resulting from enabling the
>>> -Wunused-value compiler option on linux.
>>>
>>> The patch was initiated by Jeremy (jeremymanson at google.com).
>>> More changes are needed for it to pass the build.
>>>
>>> Tests performed:
>>> jprt
>>> jtreg on linux_x64
>>> vm.quick on linux_x64
>>>
>>> Webrev: http://cr.openjdk.java.net/~ccheung/8014431/webrev/
>>> Bug: http://bugs.sun.com/view_bug.do?bug_id=8014431
>>>
>>> thanks,
>>> Calvin
>