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

[Philip Race]

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
>
>