zlib configuration : system vs. bundled

[Baesken, Matthias]

Hi Alan,   thanks for the  info .
Are you aware of  a way to  reliably   see  the info   (e.g. in hs_err  file)   what version of  libz  was used  at runtime ?

On linux (with some luck )   we see it in hs_err  , at least a lot of distros  put the version into the libname , and then it is displayed  in the hs_err section 

Dynamic libraries:

 ...   /lib64/libz.so.1.2.8
...    /lib64/libz.so.1.2.8
...   /lib64/libz.so.1.2.8

On macOSX   you see nothing just because the version is not in the libname :


Dynamic libraries:

 ...  /usr/lib/libz.1.dylib


Best regards, Matthias




> -----Original Message-----
> From: Alan Bateman <Alan.Bateman at oracle.com>
> Sent: Freitag, 17. Mai 2019 09:47
> 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 16/05/2019 15:18, Baesken, Matthias wrote:
> > Hello Alan,
> >
> > I found
> >
> > http://mail.openjdk.java.net/pipermail/core-libs-dev/2015-
> March/032106.html
> >
> > and
> >
> > http://mail.openjdk.java.net/pipermail/build-dev/2016-
> February/thread.html#16602
> >
> > but without much details  on   real  or potential  performance
> improvements .
> >
> > Both discussion  threads are pretty old.  I do not think they cover  the
> changes  done in the meantime in   jdk9 and higher    in the java.util.zip
> package .
> > I think a lot of coding there moved  from C  to  Java ,  so  the libz   is used in
> JDK  less these days than  in  the "old times " .
> Yes, the ZipFile implementation has changed significantly (many of the
> motivations are listed in JDK-8142508) but the compression and checksum
> (except CRC32C) will use libz. You'll see hotspot using it too, say when
> running with -Xbootclasspath/a to add a JAR file to the boot class path.
> There has many threads here and on core-libs-dev about using the bundled
> vs. system zlib. It was an issue for the Linux distros in the early days
> of OpenJDK as they have policies to not include copies of libraries that
> the OS provides. At one point there was a patch proposing a XX option to
> select the system vs. bundled zlib at run-time, the motivation being to
> be able to switch to the Intel IPP implementation. It's impossible to
> please everyone but I think the default that we settled on is probably
> the best.
> 
> -Alan