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

[Erik Joelsson]

Hello Severin,

If adding the -lawt_headless makes the code compile with -Wl,-z,defs, 
then I would also like to see that filtering removed in the same patch. 
However, I think someone from 2d needs to shed some light on the origin 
of this. I would assume that at some point there was a reason for not 
adding -lawt_headless to libfontmanager, and for that to work, someone 
removed the -Wl,-z,defs from that linker command line. Tracing this 
back, the removal of -z defs was there in the initial Mercurial commit, 
so someone needs to go back into the really old archives to find answers 
here.

Regarding -Xlinker vs -Wl, I believe we tried to unify usage to one or 
the other at some point.

/Erik

On 2018-01-26 08:10, 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:
>
> 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