Re: [PATCH] Build libgcj, libgcj-tools, and libffi as shared libraries on Windows

["Aaron W. LaFramboise" <aaronavay62 at aaronwl dot com>]

Charles Wilson wrote:
> Why was this necessary:
>
> 	<libjava/libltdl>
> 	* ltdl.c (DLL_EXPORT): Rename to LIBLTDL_DLL_EXPORT.
> 	* ltdl.h (DLL_EXPORT): Rename to LIBLTDL_DLL_EXPORT.
>
> AFAIK, this new symbol LIBLDL_DLLEXPORT, is never defined by libtool,
> even when building libjava shared.  So the symbols decorated with
> LT_SCOPE will never get the __declspec(dllexport) annotation.
>
> Or was that the intention, in order to work around the issue where ld
> disables its default auto-export behavior, when it sees ANY symbol
> explicitly marked as __declspec(dllexport)?

Yes.  Sorry, I forgot to mention this.  In addition, we specifically do 
not want this function to be exported from the DLL at all.  See below.

> If so, then the comment:
> +#  ifdef LIBLTDL_DLL_EXPORT /* defined by libtool (if required) */
> is wrong; it should be something like
>    /* !not! 'DLL_EXPORT'; we don't want libtool to
>       automatically decorate just these exports without
>       also decorating every other libjava export
>    */

OK, I will fix this comment to reflect the purpose of this name change.

> But finally, there's one last issue: I thought one of the gcc guidelines
> going forward with respect to autotools was to NOT modify imported
> files.  These changes will be lost every time somebody resyncs with
> upstream libtool...

The new libltdl does not have this issue.  I have no idea why we're 
stuck with the 1.5 version of libltdl even though we're using a recent 
libtool.

However, libltdl seems to have been modified in similar ways by other 
people; just look at the ChangeLog.  Since everyone else is modifying 
this, and this is not an issue in the upstream version, I think this is 
the best change.

Updating to a newer libltdl would probably be good, since I suspect 
there are Windows-specific improvements in it.  However, libjava would 
need to be ported to it, since its currently dependent upon interfaces 
that have been removed in newer versions of libltdl.  There may also be 
other reasons we're still using this old version of libltdl.

> Wouldn't it make more sense, until there are proper __declspec()
> markings/macros on all desired libjava exports, to leave these source
> files alone and just explicitly use -Wl,--enable-auto-export when
> linking the libjava DLL on mingw/cygwin?

I don't like this solution as much, as these exports really are not 
dllexport, and we specifically do not want them to be exported--even 
though we are doing nothing at present to prevent this.  (As I mentioned 
previous, a future patch will fix this symbol leakage.)  For this 
reason, I think it's important we completely avoid marking these 
dllexport, beyond fixing this specific issue.

If it's all the same to you, I like my solution better. :)  Let me know 
if you still feel differently, and maybe we can talk more.