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Re: [xml] MSYS and MINGW: undefined reference to _imp__xmlFree

On 2009/11/09 at 01:26 AM, Igor Zlatkovic <igor zlatkovic com>

wrote:

On 05/11/09 12:50, Martin Schlemmer wrote:


Hi,

Sorry for the extra late reply - year end with all its deadlines, etc.


As for fixing this issue - I guess the first will be to back out

that patch 

again.  Then I

have thought about two possible solutions:
- deal with linking to static without LIBXML_STATIC defined by keep

telling 

people

to not do that.  As for the failures with xmllint, etc. I can try to

help 

debug that if I

could get more information about build environment, etc.
- rather use the approach GLIB and friends use - only allow either

static or 

shared

builds, and define LIBXML_STATIC via the headers if needed instead

of hoping

the user will remember it

Personally I thought the second approach will be the less painful in

future 

approach,

and I made a patch as well as tested it in the situations I could

think 

could cause the

failure.  I also redid the definitions in xmlexports.h to be more

like 

glib's which I think

is more clear.


If I am not wrong, when I look at your patch, that second approach
results in two sets of headers, one for the dynamic, the other for

the

static business. How should the binary distribution look like? Two
packages?


That was the idea.  Normally they would use either mostly only static
or
dynamic linking, and if they are not sure, it should not really matter.
 Just
the DLL could be another download for those that only looked for that.


One package with two sets of headers? What about that "static
for DLL", when the user builds a shared library which links to

libxml2

statically?


I will be honest if I say that I really do not know if and why this is
needed
on Windows, so I will rather refrain from answering.


Do we now have three packages or three sets of headers
there? The user will not have to define LIBXML_STATIC, but will

likely

chose a wrong package or a wrong set of headers. Nothing is won.



Ah well, like I said, I could see two ways of doing this:
- Keep saying "no don't do that"
- or just don't allow it

If the second is not appropriate, and you don't mind keeping repeating
yourself,
I do not mind trying to get it working again via another solution.


As for the rest, I am very interested in seeing a working MSYS+MinGW
build which produces libraries usable by Microsoft linker. I am
presently next to unfamiliar with GNU autoconf/automake and given my
dislike for the dreaded build system, I am likely to make myself
familiar with it only in a grave need :) I would be eternaly thankful

to

you if you could revise your patch and make the thing work with the
following constraints and freedoms:

1. Don't, under any circumstances, break the build on Linux nor

alter

the binary compatibility there or on any OS which has Unix roots.

Much

of the world, to name GNOME and KDE as prominent examples, depend on
libxml2 and they will whip our backs til the skin comes off if we

affect

them.

2. Resulting libraries must be usable by Microsoft linker. This

means

that those forsaken __declspec(dllimport/dllexport) things must be
defined properly for the build of libxml2 itself and the user code.



With all the development, etc at MSFT, you would have thought that
they
might have decided by now to try and get on with the time for
exporting
and importing symbols as well.  Especially if they did not mind
breaking
things with the needed manifest stuff for newer MSCRT, etc ....


3. You may alter the output files on Windows, such as naming them
differently (when I last tried, MSYS+MinGW produced a libxml2-2.dll,

not

the hoped for libxml2.dll). This is okay. As an orientation: If some
greedy corporation must recompile all their Windows software for the

new

libxml2 release, that I don't care about. But if Tor Lillqvist can

use

the thing for his GTK and GIMP work without having to tweak it and

thus

be able to spend more time with his children, I am all in :)



As Roumen showed, it is possible to not have the version appended by
libtool.
However, if you want it compatible with GCC and MSVC, you will have to
have
all three library extensions (.a, .dll.a and .lib), because as I
pointed out, GCC
search for .dll.a -> .a -> .lib if you did not specify static, and
without the
.dll.a and -DLIBXML_STATIC things will break ...


4. If possible, use the same set of headers for the dynamic and the
static business, even if the user has to do a -DLIBXML_STATIC for

the

static part to work. I think it is a small requirement which is

easily

met and eases the packaging of binaries.

This now sounds like a whole pile of demands and like I would love

to

see it done by someone else. Believe me, if I have had the time to

meet

the secrets of GNU autoconf/automake, I would have done it long ago.

You

seem to know your way there and can do it much more swiftly than I
could. As a remedy, don't bother with things beneath the win32
subdirectory in the source. Once your patch to autoconf/automake

based

build is complete, I'll fix the Windows scripts. Also, I can help

you

test your work and see whether my own MSYS+MinGW environment would

take it.


If this can work out, I'll do my best to adopt it for the dependants
(libxslt, xmlsec) and dependencies (zlib, iconv, openssl) and my

binary

distribution of the whole pack I shall then make with GCC, dropping
MSVC. It would be in everyone's best interest, since my binaries are
quite widely used and noone can reproduce them due to a lack of my
locally patched MSVC.

What do you think?



I have no issue if its understood that my time for the next month or
two will be very limited.

I however am a bit unclear as to what should be fixed if we keep the
dual linking approach.
As far as I am concerned, if you do things properly on a Windows host,
from 2.6.28 (last I
can track down that worked fine here without testing previous
versions), it works fine - that
is of course with that commit reverted.

http://mail.gnome.org/archives/xml/2004-February/msg00004.html 
*----------------------------------------------------------------------
This (with libxml-2.6.5) I can confirm.  I have not looked to why, but
the import library for the
DLL was never created, only the static, so when it should have linked
xmllint, etc against the
 dynamic, it used the static, and boom ....

https://bugzilla.gnome.org/show_bug.cgi?id=590302
*------------------------------------------------------
With no version information, I will either assume that it was an older
version of libxml, or
a bug with specific version of binutils and gcc 4.4.0.

https://bugzilla.gnome.org/show_bug.cgi?id=561340
*------------------------------------------------------
Not enough info, so going to assume that the static version of the
library was used without
defining LIBXML_STATIC, or it was the .lib and no .dll.a import library
issue.


What I can suggest though, is to revert the patch, and adding me to
bugs with libxml-2.7.7
(or at whatever version the patch is reverted), and making sure your
binaries include both
.lib and .dll.a (can just relink it or copy the .lib to .dll.a).  Thus
I will help to track down the
issue for later versions if any.

An alternative I have started to look at, but have not fully researched
yet, is the way both
gettext and libiconv does it (via Bruno Haible's dll magic), but I know
that for gcc-2.95.*
at least this break (think you need gcc3 or later).


So yes, I am willing, but those in charge will need to specify the
direction that they want
to go first.


Regards,
Martin


Vrywaringsklousule / Disclaimer: 
http://www.nwu.ac.za/it/gov-man/disclaimer.html
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