Re: -shared option

[Danny Smith <danny_r_smith_2001 at yahoo dot co dot nz>]

 "Ranjit Mathew" <rmathew at hotmail dot com>  wrote
> 
> ---------------------------- 8< --------------------------------
> 
> I compile this to an object file:
> 
>     gcj -c Foo.java
> 
> I now get the symbols that ought to be exported:
> ---------------------------- 8< --------------------------------
> C:\> nm Foo.o |find "T "
> 
>     00000000 T __ZN3Foo3barEv
>     0000004a T __ZN3FooC1Ev
> 
> C:\> nm Foo.o |find "D "
> 
>     00000080 D __ZN3Foo6class$E
>     00000040 D __ZTVN3FooE
> ---------------------------- 8< --------------------------------
> (getting the defined "text" and "data" symbols)
> 
> ...and create a DEF file "foo.def" with these symbols:

You need to mark DATA

> ---------------------------- 8< --------------------------------
> EXPORTS
>     _ZN3Foo3barEv
>     _ZN3FooC1Ev
      _ZN3Foo6class$E DATA
      _ZTVN3FooE DATA
> ---------------------------- 8< --------------------------------

The other way:
dlltool --output-def foo.def --export-all foo.o
and then comment out what you don't want to export.

> (Note that the leading underscores have been stripped.)
> 
> I now create the DLL using the command:
> 
>     gcj -shared -o foo.dll Foo.java foo.def
> 
> Linking against this DLL is simple:
> 
>     gcj --main=HelloWorld HelloWorld.java foo.dll
> 
> ...though the created executable directly throws a 
> NullPointerException. :-(

You can only access DATA like this

*_imp__ZTVN3FooE

so you either 
(1) need the dllimport for imported objects in client code  
(2) use --enable auto-import and (probabaly) --enable-runtime-pseudo-reloc to
fixup

Note there are fish-hooks in C++ with dllimport and virtual methods and
artificial variables (eg, typeinfo objects) generated by the compiler. I expect
the same in Java.



Danny

> 
> I'll have to investigate this a bit more...
> 
> Ranjit.
 

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