A pkg-config file for OpenJDK

[Omair Majid]

* Mario Torre <neugens at redhat.com> [2014-08-05 12:05]:
> On Tue, 2014-08-05 at 17:42 +0200, dalibor topic wrote:
> > On 04.08.2014 10:41, Mario Torre wrote:
> > > If compact profiles are an issue, I would say that OpenJDK should ship
> > > with a pkg-config for each of the profiles.
> > 
> > OK, now let's assume that multiple profiles are installed in parallel. ;)
> > 
> > Or, for a not too unusual setup, that multiple JDK/JRE versions are 
> > installed in parallel.
> > 
> > How does pkg-config pick the 'right' one to link against? Does the first 
> > one to install the OpenJDK .pc file win? The last one? Does one need a 
> > different .pc file for each major version? For each minor version?

I would expect that something like this would be handled similar to how
the selection of the correct `java` program is handled in Linux
distributions.

In case of Fedora, there would be a .pc file for each major version, and
the latest installed JDK would 'win'.

> > If I'm parsing https://bugzilla.redhat.com/show_bug.cgi?id=740762#c27 
> > right it seems that the design of the feature in the context of Fedora 
> > is still under discussion.

Yes, that's true. It looks like some people disagree that a pkg-config
file is the right solution. I would like to withdraw this patch for the
time being (and possibly resubmit if we (or other distributions) decide
it's useful).

> > > The whole point of pkg-config is to not worry about where things are
> > > installed and what the linking/flags options are, you only need to know
> > > the package name, which should be standard across distros.
> > 
> > OpenJDK 8u typically gets packaged as "openjdk-8" on Debian derived 
> > distributions, "java-1.8.0-openjdk" on Fedora derived ones, and 
> > presumably something else somewhere else.

One of the goals of this pkg-config file is to have a standard 'name':
irrespective of your distribution, there would be one name for the
pkg-config file that is decided by OpenJDK (that's us here on this
mailing list). A distribution can call their package openjdk-8.0 and it
would still use the same well-known-name for the pkg-config file.

> > In addition, the distributions tend to split OpenJDK packages in 
> > different ways - See
> > 
> >      java-1.8.0-openjdk-accessibility
> >      java-1.8.0-openjdk-demo
> >      java-1.8.0-openjdk-devel
> >      java-1.8.0-openjdk-headless
> >      java-1.8.0-openjdk-javadoc
> >      java-1.8.0-openjdk-src
> > 
> > vs.
> > 
> >      openjdk-8-dbg
> >      openjdk-8-demo
> >      openjdk-8-doc
> >      openjdk-8-jdk
> >      openjdk-8-jre
> >      openjdk-8-jre-headless
> >      openjdk-8-jre-jamvm
> >      openjdk-8-jre-zero
> >      openjdk-8-source
> > 
> > for a Fedora vs. Debian comparison.

One thing to note is that this pkg-config file is meant for those
compiling (Java and C) code. It is expected that they will need `javac`
installed. This is provided by java-1.8.0-openjdk-devel and
openjdk-8-jdk in the list above. And both those packages pull down a
working JRE too. So, even though the packages are split in funny ways,
installing the package that installs javac gets you a working JRE too,
and that's basically all you need if you are building Java code. It
should really be enough for the pkg-config file too.

Other distributions seem to use a similar packaging style: unless
there's a monolithic package, the jdk package requires the jre package
and builds on that to give everything that's required for someone who
wants to compile Java code.

> The only issue OpenJDK should probably address is the naming of itself
> in the pkg-config template, since this should likely be standard, then
> everything else will be decided at packaging level[1].
> 
> Probably Omair can help us here to better understand what OpenJDK as
> upstream could do though, since he has more packaging experience than I
> do, I would also love some feedback from the Debian packagers (or any
> other distribution that can help her).

I have cc'ed Emmanuel Bourg, who is one of the maintainers of OpenJDK 8
in Debian.

Thanks,
Omair

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