The Java Language Standard, Second Edition, Binary Compatibility spec has a
number of requirements to which gcj does not conform.
The big patch at http://gcc.gnu.org/ml/gcc-patches/2003-10/msg02003.html addreses
much of this issue, but there are still some problems, as that posting indicates.
I've added #12957 as a dependency as fixing this may involve
changing the interface to _Jv_GetJNIEnvNewFrame, and hence
impacts binary compatibility.