Re: JDK used for compiling

On Sun, 2007-11-18 at 16:37 +0100, Sven Köhler wrote:
> Hi,
> 
> if multiple JDKs are installed, which one is used for compiling
> packages? And why have you chosen that strategy?

In short build vm != system vm. That allows for the two to differ and
further choice/control.

> I was conviced, that ebuilds always use the lowest JDK version possible.
> But it seems, that packages use the System VM - which is 1.6 in my case.
> But 1.5 is also installed.

Ebuilds compile source/target based on the lowest JDK version specified
in the ebuild. Which vm is used is controlled by by the ebuild and/or
the env. But most times that's restricted just to a version that
satisfied a virtual. Not specific vms.

> So i like the idea, that, once i have troubles with 1.6, i may switch
> back to 1.5. But, there is a fair chance, that packages compiled with
> 1.6 doen't work with 1.5. And no: using "-target 1.5" is NOT sufficiant
> due to overloading.

You can switch back and forth with no problems. That's why we compile to
lowest possible source/target. If a package requires a certain version
or fails with another. It's deps will reflect that.

> So which JDK version is actually used by daemons?

System vm unless specified otherwise. Like could be done for Tomcat
in /etc/conf.d/tomcat. Which would only effect that one
service/application and not the entire system.

>  Is it the system-VM
> too? So how can i run my daemon with JDK 1.6 while compiling things
> against JDK 1.5?

If you want control over building you can edit the files
in /etc/java-config-2/build/{jdk,compilers}.conf

http://www.gentoo.org/doc/en/java.xml#doc_chap4

It can also be overridden via command line
http://www.gentoo.org/proj/en/java/java-devel.xml#doc_chap7


-- 
William L. Thomson Jr.
Gentoo/Java

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