8223944: fix zlib related building docu and comments - was : RE: zlib configuration : system vs. bundled

[Baesken, Matthias]

Btw I adjusted the build docu  and  some  m4  file comments  regarding the zlib usage :

https://bugs.openjdk.java.net/browse/JDK-8223944

http://cr.openjdk.java.net/~mbaesken/webrevs/8223944.0/


Best regards, Matthias



> -----Original Message-----
> From: Baesken, Matthias
> Sent: Mittwoch, 15. Mai 2019 10:16
> To: 'Alan Bateman' <Alan.Bateman at oracle.com>; 'build-
> dev at openjdk.java.net' <build-dev at openjdk.java.net>
> Subject: RE: zlib configuration : system vs. bundled
> 
> Hi Alan,   thanks for pointing me  at the old discussion .
> 
> http://mail.openjdk.java.net/pipermail/build-dev/2016-
> February/016602.html
> 
> talks about performance benefits .  Are you aware of some  benchmarks that
> showed the improvements ?
> 
> In reality,  if you have the latest  distro versions you might be lucky and you
> have a nice recent zlib 1.2.11  .
> However on older distros , you run in reality  into older zlibs  (often I see
> 1.2.8).  I don't think that this is a very good status .
> 
> 
> At least I think  building.md  should be fixed to  state the real status , the
> current  info is wrong :
> 
> 
> "Certain third-party libraries used by the JDK (libjpeg, giflib, libpng, lcms
> and zlib) are included in the JDK repository. The default behavior of the
> JDK build is to use this version of these libraries, but they might be
> replaced by an external version. To do so, specify `system` as the `<source>`
> option in these arguments. (The default is `bundled`)."
> 
> 
> 
> Btw  how is building.html  generated ,  is this coming from  building.md  ?
> 
> Best regards, Matthias
> 
> 
> 
> 
> > -----Original Message-----
> > From: Alan Bateman <Alan.Bateman at oracle.com>
> > Sent: Dienstag, 14. Mai 2019 17:47
> > To: Baesken, Matthias <matthias.baesken at sap.com>; 'build-
> > dev at openjdk.java.net' <build-dev at openjdk.java.net>
> > Subject: Re: zlib configuration : system vs. bundled
> >
> > On 14/05/2019 15:58, Baesken, Matthias wrote:
> > > :
> > >
> > > On the other OS platforms, in case a zlib is found on the system :
> > >
> > >    if test "x${ZLIB_FOUND}" != "xyes"; then
> > >      # If we don't find any system...set default to bundled
> > >      DEFAULT_ZLIB=bundled
> > >    fi
> > >
> > > we use it from the system .
> > > Wouldn't  it be more  consistent to  have  zlib=bundled as well as default
> for
> > the other UNIX platforms + MacOSX ?
> > > ( people who wish to use  the system zlib still can configure it )
> > >
> > > Otherwise we often run into using old zlib installations at build time which
> > might not be desired.
> > >
> > It was a deliberate change in JDK 9 to use the system zlib if possible.
> > Windows is the outlier. If you through the archives of core-libs-dev
> > then you should find several discussions about this, I think the most
> > recent was in 2016, subject line "JDK-8031767 Support system or
> > alternative implementations of zlib".
> >
> > -Alan