RFR (XXS): 8208672: Enable -Wreorder in make files

[David Holmes]

Hi Thomas,

On 7/08/2018 7:34 PM, Thomas Schatzl wrote:
> Hi David,
> 
> On Tue, 2018-08-07 at 07:17 +1000, David Holmes wrote:
>> Hi Thomas,
>>
>> On 6/08/2018 10:38 PM, Thomas Schatzl wrote:
>>> Hi David,
>>>
>>> On Fri, 2018-08-03 at 10:20 +1000, David Holmes wrote:
>>>> Hi Thomas,
>>>>
>>>> On 2/08/2018 7:14 PM, Thomas Schatzl wrote:
>>>>> Hi all,
>>>>>
>>>>>      there have been several suggestions to try to fix the
>>>>> Hotspot code to allow us to enable -Wreorder in the Hotspot
>>>>> sources.
>>>>> This should make problems due to use-before-initialization much
>>>>> more obvious.
>>>>>
>>>>> This change enables -Wreorder for gcc and clang.
>>>>
>>>> For Windows (VS2017+) see:
>>>>
>>>> https://docs.microsoft.com/en-us/cpp/error-messages/compiler-
>>>> warnings /c5038
>>>>
>>>> Otherwise change seems okay.
>>>>
>>>
>>> Thanks!
>>>
>>> http://cr.openjdk.java.net/~tschatzl/8208672/webrev.0_to_1 (diff)
>>> http://cr.openjdk.java.net/~tschatzl/8208672/webrev.1 (full)
>>>
>>> I verified that all our platforms (including Windows) still build.
>>
>> I think the Windows change needs to be based on the compiler version
>> used as, from what I read, the flag only exists in VS2017.
> 
>    jdk11 official compiler is VS2017 so I figured it would not be that
> much of a problem.

Right now the build supports a range of compilers for the community:

################################################################################
# The order of these defines the priority by which we try to find them.
VALID_VS_VERSIONS="2017 2013 2015 2012 2010"

> Another reason for my thinking is that MSVC 2013 does not implement
> some interesting C++11 features anyway so we might be forced to drop
> support for it soon (and the situation is of course worse if we upgrade
> to C++14).

If that happens we'd have to deal with it sure ...

> I looked a bit at the makefile and conditionalizing this on VS2017 (or
> checking only whether VS2013 let it slide, i.e. give an "unsupported
> option" warning but continue anyway because I would need to setup a
> Windows dev environment somewhere) would take me a lot of time.

Hoping the build folk will jump in as this should be pretty 
straight-forward I think - just a question of knowing what VERSION 
variable to test.

> Would it be possible to skip -Werror support for Visual Studio now and
> try to fix this in a later enhancement?

Sure. Just a pity as it will be 10x as much work to add later by itself.

Thanks,
David
-----

> Thanks,
>    Thomas
>