[OpenJDK 2D-Dev] [REGRESSION?] Build warnings at jdhuff.c with GCC 6

[Erik Joelsson]

Hello,

I do agree that maintaining the list of disabled warnings will be  
impossible unless we have a structured way of tracking for which  
compiler versions we disable what. Ideally we should be able to easily  
add conditions for when certain warnings should be disabled. We are  
unfortunately lacking that today and at least I don't have the bandwidth  
to fix that anytime soon.

The official compilers are only really official for Oracle. The OpenJDK  
can (and should) be buildable with a much wider range of compiler  
versions. Luckily we have the workaround of setting  
--disable-warnings-as-errors when this situation occurs.

For reference, the compilers Oracle uses are listed in README-builds.md  
in the top level directory in the forest.

So for now at least, I think Phil is right.

/Erik

On 2016-08-23 17:11, Philip Race wrote:
> Erik .. please chime in if you disagree with the following
> The goal here is to have no warnings with the *official* compilers.
> If you are using something else and get warnings then either fix
> the *source* or else you need to use --disable-warning-as-errors.
>
> Otherwise we'll be suppressing the warnings for a whole range
> of compilers and no one will know what the set is and these
> bugs will become 'unfixable' and a continual chore of churn.
> It will be something we should address as we move *official* compilers.
>
> In fact the warning you want to suppress is one I just got rid of (the
> suppression)
> http://hg.openjdk.java.net/jdk9/client/jdk/rev/d4f7412a51d2
> I don't think we want to add it back unless the *official* compilers object
> .. I am sure that official list is documented somewhere.
>
> -phil.
>
>
> On 8/23/16, 6:10 AM, Yasumasa Suenaga wrote:
>> Hi all,
>>
>> I've fixed several warnings when we build OpenJDK with GCC 6 in
>> JDK-8160294.
>> However, I encountered shift-negative-value warnings at jdhuff.c on my
>> Fedora 24 (GCC 6.1.1):
>> --------------
>> /home/ysuenaga/OpenJDK/hs/jdk/src/java.desktop/share/native/libjavajpeg/jdhuff.c:458:13:
>> warning: left shift of negative value [-Wshift-negative-value]
>> { 0, ((-1)<<1) + 1, ((-1)<<2) + 1, ((-1)<<3) + 1, ((-1)<<4) + 1,
>> ^~
>> /home/ysuenaga/OpenJDK/hs/jdk/src/java.desktop/share/native/libjavajpeg/jdhuff.c:458:28:
>> warning: left shift of negative value [-Wshift-negative-value]
>> { 0, ((-1)<<1) + 1, ((-1)<<2) + 1, ((-1)<<3) + 1, ((-1)<<4) + 1,
>> ^~
>> /home/ysuenaga/OpenJDK/hs/jdk/src/java.desktop/share/native/libjavajpeg/jdhuff.c:458:43:
>> warning: left shift of negative value [-Wshift-negative-value]
>> { 0, ((-1)<<1) + 1, ((-1)<<2) + 1, ((-1)<<3) + 1, ((-1)<<4) + 1,
>> :
>> --------------
>>
>> I think these warnings are available from JDK-8074827.
>> This issue enables warnings to fix in the source code.
>> However, in review of JDK-8160294, I heared that warnings in IJG JPEG
>> library should just be suppressed:
>>
>> http://mail.openjdk.java.net/pipermail/jdk9-dev/2016-June/004497.html
>>
>>
>> So I think they should be suppressed and we should fix as below:
>> --------------
>> diff -r b548b8217d8c make/lib/Awt2dLibraries.gmk
>> --- a/make/lib/Awt2dLibraries.gmk Mon Aug 22 19:28:36 2016 -0700
>> +++ b/make/lib/Awt2dLibraries.gmk Tue Aug 23 22:08:44 2016 +0900
>> @@ -490,7 +490,7 @@
>> CFLAGS := $(CFLAGS_JDKLIB) $(BUILD_LIBJAVAJPEG_HEADERS) \
>> $(LIBJAVA_HEADER_FLAGS) \
>> -I$(SUPPORT_OUTPUTDIR)/headers/java.desktop, \
>> - DISABLED_WARNINGS_gcc := clobbered, \
>> + DISABLED_WARNINGS_gcc := clobbered shift-negative-value, \
>> MAPFILE := $(JDK_TOPDIR)/make/mapfiles/libjpeg/mapfile-vers, \
>> LDFLAGS := $(LDFLAGS_JDKLIB) \
>> $(call SET_SHARED_LIBRARY_ORIGIN), \
>> --------------
>>
>> If it is correct, I file it to JBS and upload webrev.
>> Do you think about it?
>>
>>
>> Thanks,
>>
>> Yasumasa
>>
>>