gjdoc does ship its own launch script, which doesn't provide any means to pass arguments directly to the java vm, instead of to the launched application. Because of this, it is impossible to comtrol the heap limit of a gjdoc invocation, which causes bug #292534 to persist for me. I suggest gjdoc drop its own launch script and use the one provided by java-pkg_dolauncher instead.
Fixed in 0.7.9-r2, thanks