Re: Static executables

[Andrzej Bialecki <ab at getopt dot org>]

Per Bothner wrote:
> Andrzej Bialecki wrote:
> > Tom Tromey wrote:
> >
> > > > > > > > "Andrzej" == Andrzej Bialecki <ab@getopt.org> writes:
> > > > > > > >             
> > >
> > >
> > > Andrzej> The question is: is it possible to build static binaries on 
> > > Linux/BSD,
> > > Andrzej> and if yes, what is the right incantation to do this, for 
> > > input files
> > > Andrzej> consisting of a mix of *.java, *.jar, and JNI *.o objects? 
> > > Eg. if I'm
> > > Andrzej> using Fedora Core 4, which sports gcc 4.0.2, whenever I try 
> > > to pass
> > > Andrzej> the -static flag, the compiler complains that static 
> > > compilation is
> > > Andrzej> not supported.
> > >
> > > Funny, I didn't realize that this error was in there.
> > > I don't remember this decision.
> > >
> > > Andrzej> * it's not supported, because it's broken in some 
> > > well-defined cases
> > >
> > > Any code that uses reflection will not work properly.  This is a
> > > problem because parts of the core class library depend on reflection.
> > > For instance, character set translators and locales are loaded this
> > > way.
>
> That may be somewhat misleading.  It's not reflection per se that is
> the problem, but dynamicaly loading classes.  I.e. anytime you load
> a class using Class.forName may fail unless you're sure the class
> is in the static executable.  The static linker can't tell which
> classed might be loaded using Class.forName.

Ah, that's much better news. I happen to know which classes I'm going to 
load dynamically in my code, and also in all libraries that I use (I 
hope I know this ..).

> > Ugh, that's pretty serious ... Ok, then this means that it's not 
> > possible to redistribute binaries to machines where there is no 
> > runtime installation. :-( Or at least not as a single file.
>
> Er, no, it's possible.  Just tricky.  And more-or-less unsupported.
>
> > If I were to have the libgcj.a (I don't think it's installed by 
> > default), could I pick by hand some of the .o files from it and 
> > explictly tell the linker to keep all symbols from those files? Would 
> > it work then? Or keep all symbols from the whole libgcj (and tell 
> > linker to ignore duplicates), would this work?
>
> Yes, some variation of that can be made to work.

Do I need to compile the libgcj.a from source, or is it distributed as a 
package (rpm?). If from source, are there any particular options to 
./configure I should be aware of?

> A simple kludge: In your main file do something like:
>
>   static void dummy () {
>     Class myclass1 = mypackage.MyClass1.class;
>     ... etc ...
>   }
>
> or:
>   static final Class myclass1 = mypackage.MyClass1.class;
>
> I don't guarantee that this will actually work - but it is something
> that probably *should* work, and shouldn't be very difficult to make
> work if it doesn't.

Yep, I get it now, I just need to reference the class explicitly in my 
code, otherwise linker will skip it. Makes sense.

Thank you for your help!

--
Best regards,
Andrzej Bialecki     <><
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