[OpenJDK 2D-Dev] RFR: JDK-8196218: [linux] libfontmanager should be linked against headless awt library

[Erik Joelsson]

On 2018-01-26 08:44, Phil Race wrote:
> When this was fixed for Solaris 
> https://bugs.openjdk.java.net/browse/JDK-8071710
> the observed problem was not building (although it could have been) 
> but at runtime.
> I think you can verify what you've done with "ldd" ..
>
> This patch adds awt_headless.so, but does not remove awt.so.
>
> Perhaps the line
>
> LIBS_unix := -lawt -ljava -ljvm $(LIBM) $(LIBCXX)
> After your fix I expect "ldd" should not need to show awt .. just 
> awt_headless
>
> ie linux should not have this -lawt dependency any more and the -lawt 
> dependency should be specific to windows + mac ..
>
So we already use -lawt_headless on solaris and aix, then I really can't 
see a reason not to do the same for linux.
>
> On 01/26/2018 08:10 AM, Severin Gehwolf wrote:
>> Hi,
>>
>> Could I please get a review for this rather small patch which
>> originally occurred for us on JDK 8 (Fedora) which recently switched to
>> building with "-Wl,-z,defs" linker flags. The result was a build
>> failure, due to unresolved symbols. Indeed libfontmanager.so should
>> have -lawt_headless in the list of dependent libs as symbols such as
>> AWTLoadFont come from libawt_headless.so, not libawt.so on Linux. Some
>> more details are on the bug.
>>
>> webrev: 
>> http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8196218/webrev.01/
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8196218
>>
>> Testing: Build fails with configure option
>>           --with-extra-ldflags="-Xlinker -z -Xlinker defs"
>>           prior the fix. Succeeds after.
>>
>> Question for 2d-folks/build-dev folks:
> I don't know about this, build folks probably know.
>
This is from way ahead of my time. The filtering is simply the 
build-infra way of achieving the same thing as in the old build system. 
Here is the corresponding code in jdk7:

$ hg annotate make/sun/font/Makefile
...
    0: #
    0: # Created without -z defs on linux
    0: #
    0: ifeq ($(PLATFORM), linux)
    0:   LDFLAGS_DEFS_OPTION =
    0: endif
...

/Erik

> -phil.
>> There is this snippet in the libfontmanager block in
>> make/lib/Awt2dLibraries.gmk, line 686:
>>
>>      LDFLAGS := $(subst -Wl$(COMMA)-z$(COMMA)defs,,$(LDFLAGS_JDKLIB)) 
>> $(LDFLAGS_CXX_JDK) \
>>          $(call SET_SHARED_LIBRARY_ORIGIN), \
>>
>> It's my understanding that this is supposed to filter "-Wl,-z,defs"
>> from LDFLAGS_JDKLIB. Does anybody know why it does so? Is there a legit
>> reason when unresolved symbols at link time are OK? Besides, why does
>> it not also filter "-Xlinker -z -Xlinker defs"? FWIW, in JDK 8 it's the
>> other way round. Xlinker flags are filtered, but -Wl,-z,defs is not.
>> Thoughts?
>>
>> Thanks,
>> Severin
>