Re: Java support in MXE build

[Michael Goffioul]

On Wed, Jul 3, 2013 at 9:45 AM, Anirudha Bose <address@hidden> wrote:

On Wed, Jul 3, 2013 at 6:51 PM, John W. Eaton <address@hidden> wrote:

On 07/02/2013 04:56 PM, Anirudha Bose wrote:

On Wed, Jul 3, 2013 at 2:18 AM, John W. Eaton <address@hidden

<mailto:address@hidden>> wrote:

    On 07/02/2013 04:38 PM, PhilipNienhuis wrote:

        By the end of the week I might have time for this.
        But I expect similar outcome as for Java, as IIRC I got exactly
        the same
        errors when building with llvm and no Java support, as when
        building with
        Java support and no llvm.


    Sorry, I haven't been following this discussion carefully.

    Are these problems for a native or cross build?

    If not cross, then has anyone attempted a cross build with Java enabled?


The problems are seen in both native as well as cross builds.

When I do a cross build for mingw, I see the following messages in
log/octave:

  configure: WARNING: JAVA_HOME environment variable not initialized.
  configure: WARNING: Auto-detection will proceed but is unreliable.
  checking for java... /usr/bin/java

  /scratch/jwe/src/mxe-octave/tmp-octave/octave-3.7.5/configure: line 66352: pwd:

  -W: invalid option
  pwd: usage: pwd [-LP]

  checking for javac... /usr/lib/jvm/java-6-openjdk-amd64/bin/javac
  checking for jar... /usr/lib/jvm/java-6-openjdk-amd64/bin/jar
  checking for Java version... 1.6.0_27
  checking for jvm.dll... ls: cannot access /usr/lib/jvm/java-6-openjdk-amd64/jre/lib/*/client: No such file or directory

  not found
  configure: WARNING: Library jvm.dll not found.  Octave will not be able to call Java methods.

Apparently jvm.dll is not available in OpenJDK. I used the Java installation from my Windows partition to get past this error.

What packages are expected to be installed in order for Octave's
configure script to enable support for Java?  It seems to me that this
is something we should be doing automatically as part of the
mxe-octave build process, not something that must be done manually
before starting the build.

Something I meant to ask Anirudha to have a look at is whether it's possible to cross-compile the octave/java support using a Linux JDK. In the end, the code is not linked to any java library, it's actually only using the headers and AFAIK, the java types are cross-platform. Some changes will be needed (see below), but I think it's worth a try.

Among the changes I foresee:

- under Linux, JNIEXPORT and JNICALL does expand to nothing; so one has to make sure the right symbols are still exported properly, maybe by overriding the macros with their Win32 definition (#define JNIEXPORT __declspec(dllexport), #define JNICALL __stdcall)

- the octave configure script will still look for jvm.dll, though I don't think it's necessary under Windows, as the JVM location will be retrieved from the Windows registry

Michael.