[OpenJDK 2D-Dev] RFR: Bug Pending: Build fails to compile jchuff.c

Erik Joelsson erik.joelsson at oracle.com
Thu Feb 1 17:05:43 UTC 2018 

Am I understanding this correctly that it's really not tied to a gcc 
version but a cpu architecture, so it's only really affecting s390x? Are 
you also saying that gcc 7.2.1 is also affected but with a different 
message? I'm fine with disabling this warning conditional on s390x, no 
need for specific gcc versions.

This discussion has already taken more time than it really warrants. :)

Regarding warning chasing. I agree that we it's not feasible to chase 
down every warning in every version of GCC, or any other toolchain, but 
I also think that for platforms/configurations where people are actively 
developing changes for OpenJDK, it makes sense to try to keep it clean. 
This helps prevent new code from introducing warnings. For the 
configurations Oracle use, we keep a strict -Werror policy because we 
want the code to be clean. I'm fine with other users trying to keep the 
same standards on their configurations, but knowing that it will be 
their responsibility to keep up to date. I also think we need to be 
reasonably fine grained in when we disable warnings. Specifying every 
affected version of a toolchain is too much, but if there are specific 
well defined limits to where the disabling relevant, then I think we 
should use them, within reason. This also helps with keeping track of 
why a particular warning is disabled in a future attempt to fix them.

On the other hand, if you are just building OpenJDK to produce binaries, 
without producing and up streaming new code changes, there really isn't 
much need for making the effort of trying to keep things clean, and 
trying to do so will likely just end up being more work than it's worth.

/Erik


On 2018-02-01 03:36, Adam Farley8 wrote:
> Hi All,
>
> After doing some experimenting, I've discovered the problem isn't 
> limited to
> SLES, or gcc 4.8.5, or zLinux.
>
> Platforms affected: zLinux, ppcle Linux
> Platforms not affected: x86 Linux
>
> gcc versions affected: 4.8.5, 5.4.0
> gcc versions unaffected: 7.2.1
>
> linux variations affected: Ubuntu, SLES
> E.g. when I told SLES 12 (zLinux) to install gcc, it installed 5.4.0.
>
> All this tells me that, if we intent to encourage SLES 12 users to build
> Java 11, we need this warning suppression hard coded. There are ways to
> do "greater than"s and "first character in"s in make, but they require
> either shell commands, or more dollar signs than you can shake a stick 
> at.
>
> I propose we hard code "array-bounds" into javajpeg's 
> DISABLED_WARNINGS_gcc
> for all java versions, and move on.
>
> On the basis that gcc 7.2.1 produces a different error message when an
> array-bounds problem occurs (e.g. frog[-1] produces the warning
> "error: ‘frog[-7]’ is used uninitialized in this function"), I don't see
> leaving array-bounds in DISABLED_WARNINGS_gcc as a problem.
>
> Thoughts?
>
> Best Regards
>
> Adam Farley
>
> > The claim on the wiki was made by Volker on July 13 2017. It was done on
> > SuSE linux while the reported problem is on zLinux. Maybe they have
> > different vendor specific patches in their respective gcc builds? Is SAP
> > still able to build without --disable-warnings-as-errors? This wiki is
> > supposed to be a community effort.
> >
> > /Erik
> >
> >
> >On 2018-01-24 16:37, David Holmes wrote:
> >> Hi Magnus,
> >>
> >> On 25/01/2018 9:55 AM, Magnus Ihse Bursie wrote:
> >>> I'm not sure I'm able to follow where this discussion is heading, but
> >>> at the very least I'd like to chime in on the patch below:
> >>>
> >>> I don't like how the entire DISABLED_WARNINGS_gcc line is lifted out.
> >>> A better solution is something like this:
> >>>
> >>> ifeq ($(CC_VERSION_NUMBER), 4.8.5)
> >>>   #Turn off array-bounds warnings for libjava compilation because
> >>> jchuff.c
> >>>   #fails to compile on gcc 4.8.5 with a warning that an array is
> >>> potentially
> >>>   #out of bounds. This kills a warnings=errors build.
> >>>   LIBJAVAJPEG_DISABLED_WARNINGS_gcc485 := array-bounds
> >>> endif
> >>> ...
> >>>     DISABLED_WARNINGS_gcc := clobbered
> >>> $(LIBJAVAJPEG_DISABLED_WARNINGS_gcc485), \
> >>>
> >>> I also can't see this going into anything else than the current
> >>> mainline, jdk/jdk i.e. JDK 11. Since the issue is trivially avoided
> >>> by using --disable-warnings-as-errors, I hardly see that it warrants
> >>> a backport.
> >>
> >> It's pointless in JDK 11 as we're not going to claim support for gcc
> >> 4.8.5.
> >>
> >> The issue is that out-of-the-box if you are building 8u or 9 and use
> >> gcc 4.8.5, which is supposed to be a valid compiler to use based on
> >> the wiki, then it fails because of this gcc bug, unless you disable
> >> warnings-as-errors. So either we put in a workaround for the bug or we
> >> update to the build docs (and/or the wiki) to make it very clear that
> >> you may need to disable warnings-as-errors (something there is no
> >> mention of in the build doc in 9).
> >>
> >> David
> >> -----
> >>
> >>> /Magnus
> >>>
> >>> On 2018-01-23 14:44, Adam Farley8 wrote:
> >>>> Hi All,
> >>>>
> >>>> All: I think I responded to everyone below. Please could a committer or
> >>>> author raise a bug and, if people are happy with this change, line
> >>>> it up
> >>>> for contribution to JDKs 8-11 (assuming 4.8.5 is still the
> >>>> recommended gcc
> >>>> for JDK10 and 11 on SUSE sles)?
> >>>>
> >>>> Erik: One toolchain-specific change, as requested. This was tested
> >>>> on JDK9,
> >>>> so please apply an offset of -1 to the line numbers before applying
> >>>> to JDK10.
> >>>>
> >>>> ----------------------- Start of Diff -----------------------
> >>>>
> >>>> diff --git a/make/lib/Awt2dLibraries.gmk b/make/lib/Awt2dLibraries.gmk
> >>>> --- a/make/lib/Awt2dLibraries.gmk
> >>>> +++ b/make/lib/Awt2dLibraries.gmk
> >>>> @@ -482,6 +482,14 @@
> >>>>   BUILD_LIBJAVAJPEG_HEADERS := $(addprefix -I, $(LIBJAVAJPEG_SRC))
> >>>>  endif
> >>>>
> >>>> +LIBJAVAJPEG_DISABLED_WARNINGS_gcc := clobbered
> >>>> +ifeq ($(CC_VERSION_NUMBER), 4.8.5)
> >>>> +  #Turn off array-bounds warnings for libjava compilation because
> >>>> jchuff.c
> >>>> +  #fails to compile on gcc 4.8.5 with a warning that an array is
> >>>> potentially
> >>>> +  #out of bounds. This kills a warnings=errors build.
> >>>> +  LIBJAVAJPEG_DISABLED_WARNINGS_gcc := clobbered array-bounds
> >>>> +endif
> >>>> +
> >>>>  $(eval $(call SetupNativeCompilation,BUILD_LIBJAVAJPEG, \
> >>>>      LIBRARY := javajpeg, \
> >>>>      OUTPUT_DIR := $(INSTALL_LIBRARIES_HERE), \
> >>>> @@ -491,7 +499,7 @@
> >>>>      CFLAGS := $(CFLAGS_JDKLIB) $(BUILD_LIBJAVAJPEG_HEADERS) \
> >>>>         $(LIBJAVA_HEADER_FLAGS) \
> >>>>  -I$(SUPPORT_OUTPUTDIR)/headers/java.desktop, \
> >>>> -   DISABLED_WARNINGS_gcc := clobbered, \
> >>>> +   DISABLED_WARNINGS_gcc := $(LIBJAVAJPEG_DISABLED_WARNINGS_gcc), \
> >>>>      MAPFILE := $(JDK_TOPDIR)/make/mapfiles/libjpeg/mapfile-vers, \
> >>>>      LDFLAGS := $(LDFLAGS_JDKLIB) \
> >>>>         $(call SET_SHARED_LIBRARY_ORIGIN), \
> >>>>
> >>>> ----------------------- End of Diff -----------------------
> >>>>
> >>>> Phil: I've changed the title as asked and supplied the diff above.
> >>>> However,
> >>>> I can't upload files to cr.openjdk.java.net, nor can I create bugs
> >>>> myself.
> >>>> I understand that authors and committers can, but I don't have those
> >>>> privileges yet. Be nice if I did. :)
> >>>>
> >>>> John: I read your email, and I understand your position. I disagree
> >>>> with it,
> >>>> but I understand it. 4.8.5 is an old version of gcc, but right now
> >>>> it is the
> >>>> listed gcc version for SUSE sles on intel, ppc, ppcle, and zLinux.
> >>>> Even if
> >>>> this is not the case for JDK 10 or 11, we should ensure this fix is
> >>>> fully
> >>>> propagated to ensure consistent behaviour.
> >>>>
> >>>> That is my position.
> >>>>
> >>>> David: Thanks for the URL. I agree with your position on 4.8.5 gcc
> >>>> needing
> >>>> to compile OpenJDK without errors or special options. :)
> >>>>
> >>>> Best Regards
> >>>>
> >>>> Adam Farley
> >>>>
> >>>>
> >>>>
> >>>> From: Phil Race <philip.race at oracle.com>
> >>>> To: Adam Farley8 <adam.farley at uk.ibm.com>, 2d-dev at openjdk.java.net
> >>>> Cc: build-dev <build-dev at openjdk.java.net>
> >>>> Date: 18/01/2018 19:16
> >>>> Subject: Re: [OpenJDK 2D-Dev] [PATCH] Build fails to compile jchuff.c
> >>>> ------------------------------------------------------------------------
> >>>>
> >>>>
> >>>>
> >>>>
> >>>> Try again with build-dev cc'd ..
> >>>>
> >>>> -phil.
> >>>>
> >>>> On 01/18/2018 11:14 AM, Phil Race wrote:
> >>>> I agree with what Erik said on build-dev that being specific about
> >>>> the tool chain
> >>>> and the reason are worthwhile and important. We've done that in
> >>>> similar cases.
> >>>>
> >>>> Also these review threads usually should have a subject like
> >>>> RFR: <BUG ID>: <Bug Synopsis>
> >>>>
> >>>> which means you first need a bug id .. the patch can't be pushed
> >>>> without one anyway.
> >>>>
> >>>> Then the patch should be an in-line diff or a webrev hosted on
> >>>> cr.openjdk.java.net.
> >>>>
> >>>> I think in-line would be OK for this small change.
> >>>>
> >>>> -phil.
> >>>>
> >>>> On 01/17/2018 09:30 AM, Adam Farley8 wrote:
> >>>> Hi All,
> >>>>
> >>>> Under these circumstances, jchuff.c will not compile:
> >>>>
> >>>> Platform: zLinux (s390x)
> >>>> Release: JDK9 (may affect other JDKs).
> >>>> GCC Version: 4.8.5
> >>>> Notes: --disable-warnings-as-errors suppresses this error.
> >>>>
> >>>> The error is:
> >>>>
> >>>> /home/adamfarl/hotspot/jdk9/jdk/src/java.desktop/share/native/libjavajpeg/jchuff.c:
> >>>>
> >>>> In function 'jGenOptTbl':
> >>>> /home/adamfarl/hotspot/jdk9/jdk/src/java.desktop/share/native/libjavajpeg/jchuff.c:808:18:
> >>>>
> >>>> error: array subscript is below array bounds [-Werror=array-bounds]
> >>>>      while (bits[j] == 0)
> >>>>                 ^
> >>>>
> >>>> This is a continuation of a conversation in the build-dev mailing
> >>>> list, if anyone wants to
> >>>> check the history.
> >>>>
> >>>> The short version is that, while you *can* suppress the problem by
> >>>> adding
> >>>> --disable-warnings-as-errors to your configure step, I posit that a
> >>>> builder shouldn't
> >>>> have to.
> >>>>
> >>>> Various solutions were debated. One involves changing
> >>>> Awt2dLibraries.gmk.
> >>>>
> >>>> Basically you change line 494 to this:
> >>>>
> >>>>    DISABLED_WARNINGS_gcc := clobbered array-bounds, \
> >>>>
> >>>> I'm running a build now to check that works, but basically we should
> >>>> end up with a
> >>>> -Wno-array-bounds on the gcc compile command for jchuff.c, thereby
> >>>> ignoring the warning.
> >>>>
> >>>> A smarter variant involves checking for that specific version of the
> >>>> gcc, but that seems
> >>>> wordy to me for this problem. Keeping it simple. :)
> >>>>
> >>>> 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
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>> 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
> >>>
> >
> >
> >
>
> 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

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