RFR: JDK-8074859 Turn on warnings as error

Volker Simonis volker.simonis at gmail.com
Wed May 20 09:50:09 UTC 2015


I'm a little confused about this change. I finally found some time to
look at it, because it makes most of our nightly jdk9/dev builds fail.
Now I've looked at the 'simplest possible failure' which happens on
linux/amd64. The failure is the following:

error: comparison of unsigned expression >= 0 is always true

First I thought this is because we are using a different version of
GCC but I've just verified that this warning which is now turned into
an error happens with all version of GCC starting from at least 4.3 up
to 4.8.

So do you do your regular builds on linux/amd64 by default with
"--disable-warnings-as-errors" now?

Reading you first mail, the code should compile fine on the build
systems used internally at Oracle and according to
they should use gcc 4.8.2.

So what's the problem here or am I doing something wrong?

Thank you and best regards,

On Sat, May 9, 2015 at 6:30 AM, Tim Bell <tim.bell at oracle.com> wrote:
> Magnus:
> Looks good to me as well.
> Tim
> On 05/08/15 01:32, Erik Joelsson wrote:
>> Looks good.
>> /Erik
>> On 2015-05-08 09:57, Magnus Ihse Bursie wrote:
>>> On 2015-04-20 09:02, Erik Joelsson wrote:
>>>> Looks good to me.
>>> Thanks Erik.
>>> Unfortunately, I never got round to pushing this. In the meantime, the
>>> codebase evolved, and I had to add a couple of more disabled warnings. I
>>> also modified the help text on a failed build slightly.
>>> Here's the updated webrev:
>>> http://cr.openjdk.java.net/~ihse/JDK-8074859-warnings-as-errors/webrev.01
>>> /Magnus
>>>> /Erik
>>>> On 2015-04-17 14:52, Magnus Ihse Bursie wrote:
>>>>> With JDK-8074096, the number of warnings in the product was reduced to
>>>>> a minimum. This enables the next step, which is turning on the respective
>>>>> compiler flags that turns warnings into errors. In the long run, this is the
>>>>> only way to keep the warnings from creeping back.
>>>>> Even with JDK-8074096, the product does not build 100% warning free.
>>>>> This is due to some warnings that cannot be disabled, or (in one case) where
>>>>> C and C++ code is mixed, and warnings for both languages cannot be used. A
>>>>> system similar to the one introduced in JDK-8074096 is therefore needed, in
>>>>> which individual libraries can be exempted from this flag, until such
>>>>> warnings are fixed. A library can thus disable warnings as errors with
>>>>> WARNINGS_AS_ERRORS := false, or (better) use a toolchain-specific version,
>>>>> e.g WARNINGS_AS_ERRORS_gcc := false. This is intended as a temporary
>>>>> measure, though. The long-term solution is reasonably to fix the warnings
>>>>> and remove that argument.
>>>>> Also, different versions of compilers can generate a different set of
>>>>> warnings. It is therefore necessary to be able to turn off this globally.
>>>>> Therefor a new flag for configure is introduced:
>>>>> --disable-warnings-as-errors.
>>>>> While the code compiles without errors on the build systems used
>>>>> internally at Oracle, this might not be the case on other combinations of
>>>>> operating system versions and toolchain versions. To facilitate for
>>>>> unexpecting developers, a help message is added if the build fails, that
>>>>> suggests using --disable-warnings-as-errors. This solution was chosen as a
>>>>> compromise between the "hard core" solution of turning on warnings as errors
>>>>> by default for anyone, and the cowar... erm, conservative solution of
>>>>> checking if the compiler versions exactly match what's used inside Oracle
>>>>> (and therefore regularly tested), and only turn it on in that case.
>>>>> Similarly to JDK-8074096, I intend to file follow-up bugs for each
>>>>> individual library that got a WARNINGS_AS_ERRORS_* := false.
>>>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8074859
>>>>> WebRev for top:
>>>>> http://cr.openjdk.java.net/~ihse/JDK-8074859-warnings-as-errors-top/webrev.01
>>>>> WebRev for jdk:
>>>>> http://cr.openjdk.java.net/~ihse/JDK-8074859-warnings-as-errors-jdk/webrev.01
>>>>> Some comments:
>>>>> * I needed to add a few more DISABLED_WARNINGS. For windows, this is
>>>>> most likely due to the recent compiler change. For other libraries, I'm not
>>>>> sure, but it might well be the result of recent changes that has introduced
>>>>> new warnings. If so, it highlights the need of this patch to keep the build
>>>>> warning free.
>>>>> * For a few libraries and toolchains, there is *both*
>>>>> WARNINGS_AS_ERRORS := false and a DISABLED_WARNINGS list. This is the case
>>>>> if not all warnings are possible to disable.
>>>>> * I have removed some incorrect uses of SHARED_LIBRARY_FLAGS. This is
>>>>> included in our JDK LDFLAGS, so it should not be set separately, and
>>>>> definitely not as CFLAGS. (This caused compiler warnings, which now turned
>>>>> into errors.) However, a more suitable long-term solution is probably to
>>>>> move the knowledge of how to create shared libraries more specifically into
>>>>> SetupNativeCompilation, and not set it as part of the JDK flags.
>>>>> /Magnus

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