Calling java code from C/C++ code.

Mon Mar 5 14:03:00 GMT 2001

It's essential that when the gc is loaded, the weak reference to data_start
be bound to the definition from the main executable.
The dlopen man page vaguely implies that this might happen if you link the
main program with "-rdynamic", which I couldn't find on the ld man page.
Probably the easiest workaround is to explicitly link against the GC library
instead of using dlopen to load it. A GNU ld expert might be able to
suggest better solutions.
Hans
> -----Original Message-----
> From: Timothy Wall [ mailto:twall@oculustech.com ]
> Sent: Monday, March 05, 2001 1:49 PM
> To: Boehm, Hans
> Cc: Bryce McKinlay; java@gcc.gnu.org
> Subject: Re: Calling java code from C/C++ code.
>>> This is linux x86, RedHat 7.0, using gcc 3.0 branch from CVS, 
> and binutils
> from the distribution. The java code is very simple:
>> public class test {
> public static void execute() {
> main(new String[0]);
> }
> public static void main(String[] args) {
> System.out.println("Hello, world");
> System.exit(0);
> }
> }
>> I believe dlopen loads the gc, using LD_LIBRARY_PATH to find 
> it. I have no
> idea how that affects the weak references.
>> Tim
>> "Boehm, Hans" wrote:
>> > > -----Original Message-----
> > > From: Timothy Wall [ mailto:twall@oculustech.com ]
> > > (gdb) p GC_dump()
> > > ***Static roots:
> > > From 0x0 to 0x804a1d8
> > >
> > ...
> > There's the problem. The collector thinks that static data 
> for the main
> > program starts at location 0, and hence it's trying to scan 
> memory from 0x0
> > to 0x804a1d8. Most of that isn't mapped.
> >
> > I assume your gcj installation works with a simple 100% 
> Java program? This
> > is Linux/X86? Which distribution?
> >
> > Does the garbage collector itself get loaded with a dlopen? 
> Does that
> > affect processing of the weak references to __data_start 
> and data_start?
> >
> > Hans
>