Hi Erik, Phil,
Thank you for replying.
I understand background of JDK-8074827.
In this particular case is shift-negative-value a new warning in GCC 6?
Yes, this feature is implemented GCC 6:
https://gnu.wildebeest.org/blog/mjw/2016/02/15/looking-forward-to-gcc6-many-new-warnings/
BTW, why is libjavajpeg only enabled these warnings?
For example, liblcms is disabled format-nonliteral, type-limits, and
misleading-indentation.
I agree compiler warnings is very useful to fix. However, I think a part of
source of libjavajpeg is third-party (developed by Independent JPEG Group).
According to [1], warnings in this library should be suppressed.
If all binaries which are included in JDK/JRE should be enabled all compiler
warnings, I think LCMS and any other libraries should be fixed.
Which policy is correct?
Thanks,
Yasumasa
[1] http://mail.openjdk.java.net/pipermail/jdk9-dev/2016-June/004495.html
On 2016/08/24 18:48, Erik Joelsson wrote:
Hello,
On 2016-08-23 18:12, Phil Race wrote:
On 08/23/2016 08:47 AM, Erik Joelsson wrote:
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.
I agree there. This is fortunately not an "unbuildable" situation.
The only other option I can think of which may or may not be palatable
is to explicitly
check the compiler version and add that disabled warning only for that
exact compiler version.
There'd still be some maintenance as that compiler version became either
official .. or obsolete ..
Is there precedent (or any kind of support) for that ?
What I had in mind was a structured way of adding conditionals for some kind of ranges of
compiler versions, or at least something like 6.*, or "greater than 4.9.3".
It's pretty simple today to check for exact compiler versions but then we end up with a
lot of changes when minor versions are bumped. I don't think that would be worth it.
In this particular case is shift-negative-value a new warning in GCC 6? If
that's the case it doesn't actually hurt adding it since GCC is nice enough to
not complain about unknown warning tags. If we do, just make sure to specify in
a comment that it's specific to GCC version 6+.
/Erik
-phil.
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
