RFR: 8003310: Enable -Wunused when compiling with GCC

[Mikael Vidstedt]

I've been waiting for Joe's changes to bubble up so as to not add a 
conflict unnecessarily, and since they're now in hotspot-rt I have 
uploaded a webrev for what I hope is a final time *knocking on wood*. I 
would appreciate a quick check to see that everything still looks fine:

http://cr.openjdk.java.net/~mikael/webrevs/8003310/webrev.08/webrev/

The only relevant changes from the last webrev should be:

make/linux/makefiles/gcc.make:

* Eliminate the ADDITIONAL_WARNINGS variable and just use WARNING_FLAGS 
directly
* Clean up the -Wconversion logic

src/share/vm/runtime/arguments.cpp:

* Updated after the recent changes to SERIAL/INCLUDE_ALL_GCS (8005915)

Thanks,
Mikael

On 2/21/2013 7:16 PM, David Holmes wrote:
> One final comment - please liaise with Joe Provino who is adding 
> -Wundef so we can get a consistent approach as to where these -Wxxx 
> flags get added. :)
>
>
> (Don't know what I was looking at with the trace_locking stuff - it 
> ends up as an empty method.)
>
> David
>
> On 22/02/2013 6:00 AM, Mikael Vidstedt wrote:
>>
>> On 2013-02-20 10:04, Coleen Phillimore wrote:
>>> On 2/20/2013 12:33 PM, Mikael Vidstedt wrote:
>>>>
>>>> On 2/19/2013 12:01 PM, Christian Thalinger wrote:
>>>>> On Feb 18, 2013, at 3:14 PM, Mikael Vidstedt
>>>>> <mikael.vidstedt at oracle.com> wrote:
>>>>>
>>>>>> A really good control question, thanks a lot for asking!
>>>>>>
>>>>>> As a matter of fact these changes are basically just doing what the
>>>>>> compiler already does for us, so it's more about cleaning up the
>>>>>> source code than reducing the size of the binary. So in theory
>>>>>> these changes should have no impact on the binary size at all, but
>>>>>> it actually turns out they do. Very specifically, the fact that I
>>>>>> moved the same_page() function from being duplicated in the three
>>>>>> os_<os>.cpp files to having it be in globalDefinitions.cpp makes
>>>>>> the binary grow a few bytes (54 bytes to be specific). The reason
>>>>>> is a bit subtle:
>>>>>>
>>>>>> The same_page() function is (was) static in the respective os_*.cpp
>>>>>> files. They are only ever used when the Verbose flag is true, and
>>>>>> furthermore the Verbose option is a develop only flag, which means
>>>>>> it is hardcoded to false in product. The compiler knows that's the
>>>>>> case and eliminates the same_page() function completely.
>>>>>>
>>>>>> Since I moved it to globalDefinitions.cpp there's no way easy for
>>>>>> the compiler to know that it is not being used, so it will actually
>>>>>> keep the function.
>>>>>>
>>>>>> Unless there are strong opinions I'm not going to do anything about
>>>>>> this.
>>>>>>
>>>>>> However, this made me question my earlier experiments with using
>>>>>> the const bool = false construct in constantPool.cpp, because after
>>>>>> all that is the exact same pattern. And it turns out that I must
>>>>>> have done something wrong when I was performing the experiments,
>>>>>> because when I do the same thing again now it turns out the
>>>>>> compiler actually *does* deadcode eliminate the debug-only
>>>>>> functions. So I take everything back and conclude that const bool =
>>>>>> false is indeed a great way to make sure the debug code does not
>>>>>> rot over time, and that the product binary will *not* contain the
>>>>>> dead functions. Sorry for any confusion this may have caused.
>>>>>>
>>>>>> With all that in mind, here's another version of the webrev:
>>>>>>
>>>>>> http://cr.openjdk.java.net/~mikael/webrevs/8003310/webrev04/webrev/
>>>>> src/share/vm/interpreter/interpreterRuntime.cpp:
>>>>>
>>>>> I suppose that #if 0 is to keep that code for...?  Could we add a
>>>>> comment why we keep it?
>>>>
>>>> This was by "popular request" (from David Holmes) :)
>>>>
>>>> I personally don't know if and how this is being used. Note that
>>>> ObjectSynchronizer::trace_locking is PRODUCT_RETURN and the
>>>> non-product implementation in synchronizer.cpp is empty (modulo the
>>>> comment saying "Don't know what to do here"), so one can question the
>>>> value of keeping the any of the trace_locking functions, but they may
>>>> be someone's favorite debugging tool. Until proven differently I will
>>>> leave it in there for now. If somebody can help me provide a useful
>>>> comment about how the code is actually being used then I will
>>>> certainly add it, otherwise I'll keep this as it is.
>>>
>>> If I remember correctly, this trace_locking code was associated with a
>>> flag that we removed a long time ago.   I don't think if we want to
>>> implement TraceLocking we'd use this function.  My vote is that it and
>>> the ObjectMonitor:: version should be removed.
>>
>> Thanks Coleen, that makes sense. I've prepared a final version of the
>> webrev with the trace_locking methods removed too:
>>
>> http://cr.openjdk.java.net/~mikael/webrevs/8003310/webrev.06/webrev/
>>
>> Any final comments?
>>
>> Cheers,
>> Mikael
>>
>>>
>>> Coleen
>>>>
>>>>> src/share/vm/oops/constantPool.cpp:
>>>>>
>>>>> So we use:
>>>>>
>>>>> + const bool debug_cpool = false;
>>>>>
>>>>> but we still have the DBG macro.  Can't we have a static debug
>>>>> method that takes all printf arguments and prints them? The
>>>>> debug_cpool should make that method empty and the compiler can
>>>>> remove it.  I really start to hate all these macros...
>>>>
>>>> I share your macro hate and I actually played around with removing
>>>> the macros just as you say. There is one small problem with doing it
>>>> that way, and that's the fact that a few of the printf:s print
>>>> symbols names, and as part of that they need to create utf8 strings
>>>> using sym->as_utf8(). The compiler can unfortunately not know that
>>>> that function is for all intents and purposes a no-op, so it will
>>>> keep the call even in product meaning increased binary size and it
>>>> will also add to the runtime since it actually performs the call and
>>>> creates the utf8 string. So I'm going to keep the macros for now.
>>>>
>>>>
>>>> I also moved the clamp_address_in_page to the globalDefinitions.hpp
>>>> header file, meaning it will be inlined and dead code eliminated.
>>>>
>>>> New webrev here:
>>>>
>>>> http://cr.openjdk.java.net/~mikael/webrevs/8003310/webrev.05/webrev/
>>>>
>>>> Final comments?
>>>>
>>>> Cheers,
>>>> Mikael
>>>>
>>>
>>