I've been looking into the problem where AOO418 can't detect older
versions of java when it is built with a new version of java. This is a
definite puzzle because the detection is done by the jvmfwk module, and
the code in that module is identical between AOO418 and trunk. The only
difference is that this module has been changed from dmake to gbuild in
trunk.
The way that java detection works is that we scan the possible java
locations, and for each we run
[path to javaa]/java[.exe] -classpath C:\\Program\ Files\\OpenOffice\
4\\program JREProperties
which is supposed to output a bunch of data about that version of java,
which we read and parse. If that fails, then we decide that version of
java is invalid or broken.
When I build AOO418 with Java 8 and it tries to detect Java 7, I see
this stack trace sent to stderr:
java.lang.UnsupportedClassVersionError: JREProperties : Unsupported major.minor
version 52.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at
java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:482)
Exception in thread "main"
The problem is that the JREProperties was compiled with Java 8, which
Java 7 can't use:
$ file /cygdrive/c/Program\ Files/OpenOffice\ 4/program/JREProperties.class
/cygdrive/c/Program Files/OpenOffice 4/program/JREProperties.class: compiled
Java class data, version 52.0 (Java 1.8)
If I build trunk with Java 8, I see:
$ file /cygdrive/c/Program\ Files/OpenOffice\ 4/program/JREProperties.class
/cygdrive/c/Program Files/OpenOffice 4/program/JREProperties.class: compiled
Java class data, version 51.0 (Java 1.7)
That's why we don't see this issue with trunk
It is possible to use a new java compiler to build for older versions of
java using the --target option, but I don't see any sign that we are
doing so.
Unfortunately the build is too silent for me to see what is actually
happening during the build. My suspicion is that somehow the trunk
build is somehow using Java 7 to build.
I see two paths forward. The first is to build with the oldest version
of java that one might want to use, which is the status quo. The second
is to somehow pass the --target option to specify an older java version
for compatibility.
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