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

[Magnus Ihse Bursie]

Quick reply from my vacation... there's a macro that tests if a compiler option is valid. We've only used it for gcc so far, but I see no reason for why it should not work with VS. Maybe you can use that instead of checking version?

I'm a bit hesitant at adding options that will produce warnings for older but still supported versions. If it's just a single compiler at the end of the list, that's one thing, but if we're talking everything but VS2017, that's another. If there's a problem adding the VS option, I'd rather see you just add the gcc one. 

/Magnus

> 7 aug. 2018 kl. 12:08 skrev David Holmes <david.holmes at oracle.com>:
> 
> 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