On 24 Sep, Don Lewis wrote:
> 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 finally figured out the difference. The 4.1.x build uses the selected
javac to build the .class file, whereas trunk and 42X use ant, and
solenv/ant/aoo-ant.xml (new to trunk ant 42X) says:
<property name="java.baseline.version" value="1.7"/>
> 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.
We could also cherry-pick the jvmfwk conversion to gbuild and the other
changes for ant.
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