<AWT Dev> JAWT Breakage in OpenJDK 7/8

Omair Majid omajid at redhat.com
Tue Jul 24 09:44:06 PDT 2012


I recently discovered that a number of applications making use of JAWT
[1] are broken on OpenJDK 7 and 8, while they were working with OpenJDK6.

The docs for JAWT state [1]:
The final step ­ the most interesting one ­ is to write the native
rendering method, with an interface that conforms to the header file
that javah generated, and build it as a standard shared library (called
myRenderingLib in the above example) by linking it, for the Solaris
operating environment, against the jre/lib/sparc/libjawt.so library.

In other words, JAWT expects third-party native libraries to be linked
against libjawt.so. However, nowhere on that page does it say that
something like System.loadLibrary("jawt") is needed. In practice, this
means that most existing applications rely on libjawt.so being magically
found and loaded by the JVM. In OpenJDK6, LD_LIBRARY_PATH was set to a
value such that the linker could resolve libjawt.so when a library
depending on it was loaded. LD_LIBRARY_PATH was removed for OpenJDK7
[2]. So a number of existing applications fail to work with OpenJDK7
because they can not load libjawt.so. Some applications have been
patched to load libjawt.so manually [3], but others haven't (or cant be).

The most backwards-compatible fix is to undo the effects of the
LD_LIBRARY_PATH change - by setting RUNPATH of the launcher, for
example. The build-dev folks suggested that I only do that as a last
resort [4].

An alternate fix seems to be to always load libjawt when awt starts up.
There might be a small window of time where a third-party library fails
to link against libjawt.so but this can happen only if awt has not
started up. I would think such a case would not work with OpenJDK6 too
since libjawt.so will not be able to resolve the dependency on
libxawt.so. libxawt.so is only loaded after awt is started up, and can
not be resolved through LD_LIBRARY_PATH.

The attached patches for OpenJDK8 and OpenJDK7 attempt this approach.
Does anyone have any thoughts or comments?

I suspect something like this might be needed for Windows too, but I
don't have access to a windows box to verify it.

As an aside, should the docs for JAWT [1] be updated?


[2] https://blogs.oracle.com/darcy/entry/purging_ld_library_path
[4] http://mail.openjdk.java.net/pipermail/build-dev/2012-July/006492.html
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