[PATCH] (Title Corrected) Build fails to compile jchuff.c using gcc 4.8.5 on zLinux

[Erik Joelsson]

This is all correct, thanks David!

For the official toolchains (basically what Oracle builds with), we very 
much like to keep warnings-as-errors active, because it's a very 
valuable tool in keeping the code healthy. For other toolchains, it 
depends, as David says.

We have a mechanism for disabling warnings for specific toolchain types 
(gcc, clang, solstudio, visualstudio) on a per library basis. We also 
have the ability to add flags globally for specific toolchain versions 
in configure, in flags.m4. If we want to solve this by disabling a 
warning due to a bug in a specific gcc version, I would recommend the 
latter.

/Erik

On 2018-01-17 14:13, David Holmes wrote:
> Adam,
>
> Erik or Magnus from the build team should step in here if this 
> information is wrong but AFAIK the intent is that using the official 
> toolchains the OpenJDK will build out-of-the-box using the supplied 
> instructions and whatever the default settings are (which ideally 
> would be without any warnings).
>
> Anyone building with a different toolchain may encounter problems, and 
> may need to disable warnings-as-errors. That should be in the build 
> docs somewhere if it isn't now.
>
> The build wiki has unfortunately not been updated for JDK 10, but we 
> didn't make any changes to the official toolchains compared to JDK 9:
>
> https://wiki.openjdk.java.net/display/Build/Supported+Build+Platforms
>
> As gcc 4.8.5 is listed as an "other build platform" I would not have 
> expected you to encounter this problem. Though it is not stated on the 
> wiki whether building on these other platforms requires changing any 
> of the build settings.
>
> If an official, or even semi-official, toolchain encounters a problem 
> then we may look into adding a toolchain specific workaround for the 
> specific file(s) affected (ie disable the specific warning). 
> Otherwise, as "John" (aka Adrian) states we don't play this game for 
> every possible toolchain that may be used.
>
> David
>
> On 17/01/2018 10:56 PM, Adam Farley8 wrote:
>> Hi John, David,
>>
>>>> If you compile jchuff.c  (part of javajpeg) without
>>>> "--disable-warnings-as-errors",
>>>> then you get an error that kills the build. This is seen in these
>>>> circumstances:
>>
>>> Last time this particular discussion came up, the conclusion was that
>>> hunting for warnings is a lost battle as the generated warnings depend
>>> heavily on the toolchain used [1,2].
>>
>>> So, I think for now we're not going to address build errors which occur
>>> when omitting "--disable-warnings-as-errors" in the configure line.
>>
>> If this is the consensus, then perhaps we should consider setting
>> --disable-warnings-as-errors by default (in the code), rather than
>> depending on the user using an option which is not part of the formal
>> build instructions.
>>
>> Thoughts?
>>
>> Best Regards
>>
>> Adam Farley
>>
>> Unless stated otherwise above:
>> IBM United Kingdom Limited - Registered in England and Wales with 
>> number 741598.
>> Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire 
>> PO6 3AU