Porting Hotspot to other platforms / OS'es

Kelly O'Hair Kelly.Ohair at Sun.COM
Thu May 22 11:31:21 PDT 2008

I have been trying to make the JDK build process work a little bit
better for potential cross compilation environments, where the native
code built can't be run on the machine doing the building.
Granted I know it isn't ideal or anywhere near perfect.
But the basic OpenJDK build, up to the point near building the demos,
does not actually run the jdk image being built.
It does run the jdk built to create the demos as I recall, and beyond that,
I tried to allow for a better cross compilation situation.

But as to an environment where a BOOT JDK is not available... humm..
It seems to me that maybe an appropriate 'ssh some_known_host' prefix
on the ant, java, javac, javah, javadoc, ... commands. So that these
could be remote runs? Just a wild thought...
I have no idea if that would work or not...


Andrew John Hughes wrote:
> On 21/05/2008, Michael Neuweiler <michael at neuweiler.biz> wrote:
>>  Hi,
>>  I wanted to start porting OpenJDK to Syllable on Intel32 but got stuck with
>> the chicken and egg problem of hotspot: "you need a running JDK to build a
>> new one".
>>  What are your recommendations to start a port? Is cross-compiling the only
>> solution or are there other ways?
>>  I think I saw once that an XSLT is started with an already installed
>> JRE/JDK during the build process on my Linux machine. Is this the only
>> reason why a JRE has to be installed?
>>  Any help would be greatly appreciated!
>>  Regards,
>>   Michael Neuweiler
> (Adding distro-pkg-dev too)
> My understanding, both from building OpenJDK quite a number of times
> and from my own general thoughts on the issues of building a Java
> environment, is that bootstrapping the JDK through its standard build
> process is more than just handling XSLT.
> The first thing you're likely to run across is that there are no
> current Java compilers (as far as I know) that are not written in Java
> -- the main two are ecj from Eclipse and javac itself.  The first
> thing the OpenJDK build process does is build javac and the other
> language tools.  The current build not only depends on an existing
> javac to do this,  but a full-scale JDK to run ant.  My personal
> feelings are that it would have been better to stick with make for the
> langtools, but oh well...
> If my memory serves correctly, this is followed by JAXWS and JAXP,
> both of which require Java.  Thus, a sensible course of action might
> be to approach building HotSpot alone first.  Assuming this is
> possible (I have my doubts about it also including Java code), you
> could then use this to run an existing JAR file containing the tools
> to build.
> The reason I've CCed distro-pkg-dev on this is that a lot of work on
> bootstrapping on unsupported architectures (mainly the CPU rather than
> the OS) has been done under the auspices of the IcedTea
> (http://icedtea.classpath.org/) project.  Here, we've found gcj to be
> useful in breaking this bootstrapping cycle -- do you know if GCC
> (which includes gcj) is available for the platform you are working on?
> This might be the simplest course of action.
> Looking forward to hearing how this works out for you,

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