[Mesa-dev] [PATCH] util/disk_cache: fix zlib linking with LTO build

[Steven Newbury]

On Sun, 2017-03-12 at 12:25 +0000, Mike Lothian wrote:
> For what its worth I compile Mesa using LTO with the gold linker so I
> don't need to specify -fuse-linker-plugin - everything works fine
> here
> 
> CFLAGS="-O3 -march=skylake -pipe -flto=8" 
> CXXFLAGS="${CFLAGS}" 
> LDFLAGS="-Wl,-O1 -Wl,--hash-style=gnu -Wl,--as-needed -Wl,-flto=8"
> 
> AR="gcc-ar" 
> NM="gcc-nm" 
> RANLIB="gcc-ranlib"
> 
> 
> On Sat, 11 Mar 2017 at 16:46 Matt Turner <mattst88 at gmail.com> wrote:
> > On Sat, Mar 11, 2017 at 7:31 AM, Emil Velikov <emil.l.velikov at gmail
> > .com> wrote:
> > > On 10 March 2017 at 13:36, Steven Newbury <steve at snewbury.org.uk>
> > wrote:
> > >> On Fri, 2017-03-10 at 12:11 +0000, Emil Velikov wrote:
> > >>> On 9 March 2017 at 14:39, Steven Newbury <steve at snewbury.org.uk
> > >
> > >>> wrote:
> > >>> > Introduction of zlib compression for the shader cache means
> > >>> > zlib needs to be explicitly linked to libOSMesa and
> > libstandalone
> > >>> > otherwise build fails when LTO is used.
> > >>> > ---
> > >>>
> > >>> How exactly are you doing the LTO build ?
> > >> I build everything LTO, except for a short blacklist where
> > >> unsupportable.  Specifically, on this system my global *FLAGS
> > contain
> > >> "-flto=8 -fuse-linker-plugin".  I have the lto linker plugin
> > symlinked
> > >> into "/usr/$CHOST/binutils-bin/lib/bfd-plugins/".
> > >>
> > >> I also have have the following env vars set to ensure they are
> > called
> > >> with the LTO plugin:
> > >> AR="gcc-ar"
> > >> NM="gcc-nm"
> > >> RANLIB="gcc-ranlib"
> > >>
> > > One should not need these. Have you checked that the issue is
> > > reproducible w/o them ?
> > 
> > I think they are necessary
> > 
> > https://gcc.gnu.org/ml/gcc-help/2012-03/msg00100.html
> > 
> > (though I don't know under which circumstances precisely)
> > 
> > FWIW, I agree that this patch looks like a hack.

My fault.  I've a local patch which caused LIBADD to be defined twice
in the src/util/Makefile.am which caused -lz not to be applied to the
linking of libmesautil.la.  So my patch is indeed wrong, or at least
unnecessary.  Interesting that missing symbols showed up where they
did, in particular with OSMesa.

Apologies.
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