[xml] Re: Building libxml2 as a DLL under MinGW MSYS (Igor Zlatkovic)

[Eric Zurcher csiro au]

Hi,

I've recently recompiled libxml2 2.4.23 using Borland's C++ Builder 6, and
after struggling with that I would have to say that one of Elizabeth
Barham's suggestions for MinGW seems very reasonable to me. Specifically, I
think that adding "LIBXML_DLL_IMPORT" to ALL exported functions and
variables makes things a lot simpler than having to deal with the process of
generating a .DEF file. I don't see how it would "break" the current build.
It is fairly simple to define this symbol so that it expands to
"__declspec(export)" when building the DLL, to "__declspec(import)" when
building an application linking to the DLL, and to "" (that is, to an empty
string) when building a static library. (Of course, on most other platforms,
LIBXML_DLL_IMPORT would simply expand to an empty string). This seems far
simpler than the current mechanism of creating (manually?) libxml2.def.src,
then generating a .DEF file from that. Am I missing something?

Also, the macro __WIN32__ is indeed predefined in BCB6. WIN32 and _WIN32 are
not.


> -----Original Message-----
> From: Igor Zlatkovic <igor stud fh-frankfurt de>
> Cc: <xml gnome org>
> Subject: Re: [xml] Building libxml2 as a DLL under MinGW MSYS
> Date: Wed, 25 Sep 2002 16:47:27 +0200
> Organization: UAS Frankfurt
>
> Hi there,
>
>
> > include/libxml/entities.h
> > include/libxml/parser.h
> >   - Added 'LIBXML_DLL_IMPORT' to all function definitions
> >     for replacement with __declspec(dllimport) or
> >     __declspec(dllexport) as needed.
>
> That would break the current build with MS compiler. As 
> things fare, that
> dllexport while compiling libxml would produce a static library which
> reexports all those symbols from the client program. GCC can 
> automatically
> export all nonstatic symbols, so I would suggest to either 
> use that feature
> or a .DEF file.
>
> > include/libxml/tree.h
> >   - Same as above
> >   - Replaced
> > #if defined(WIN32) && (defined(_MSC_VER) || defined
> > (__BORLANDC__))
> >     with
> > #if defined(__WIN32__)
> >     since MinGW compiler doesn't define either of these.
>
> Neither Borland nor Microsoft #define __WIN32__, so that 
> change would break
> both compilers.
>
> > include/libxml/xmlversion.h
> >   - disabled libiconv
>
> That file is autogenerated and modifying it brings nothing. 
> Besides, perhaps
> should the user be the one who decides if she needs iconv or not.
>
> > I realize that not all of the changes may require
> > modification so as to not change any already existing
> > functionality, but as they stand, they comprise a
> > sufficient set to allow one to build libxml under MSYS.
>
> Unfortunately, these modifications break other platforms.
>
> There is at least one more person who marches under the same banner. I
> suggest you and Elisabeth cooperate in making MSYS/mingw 
> work, it would be
> the most productive way.
>
> Ciao
> Igor
Eric Zurcher
CSIRO Livestock Industries
Canberra, Australia
Eric Zurcher csiro au