Hi,

Recently a change was done to attempt to fix bug 590302 and 561340. This was done at http://git.gnome.org/cgit/libxml2/commit/?id=a194ccb8d19ddde94c2c04ddf197e6a629f7cc9b

Unfortunately a regression was introduced by this change. When using the (Fedora) MinGW (cross-)compiler the compilation of C++ source code which require libxml2 headers always fails. Here's a simple testcase:

-----------

#include <libxml/parserInternals.h>

int main()
{
    return 0;
}

-----------

Here's the complete GCC output when trying to compile this as C++ code:

$ i686-pc-mingw32-g++ testxml.cc -o testxml.exe -I/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/
In file included from /usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/parserInternals.h:18,
                 from testxml.cc:1:
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/chvalid.h:80: error: external linkage required for symbol 'xmlIsBaseCharGroup' because of 'dllexport' attribute
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/chvalid.h:80: error: uninitialized const 'xmlIsBaseCharGroup'
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/chvalid.h:124: error: external linkage required for symbol 'xmlIsCharGroup' because of 'dllexport' attribute
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/chvalid.h:124: error: uninitialized const 'xmlIsCharGroup'
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/chvalid.h:136: error: external linkage required for symbol 'xmlIsCombiningGroup' because of 'dllexport' attribute
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/chvalid.h:136: error: uninitialized const 'xmlIsCombiningGroup'
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/chvalid.h:156: error: external linkage required for symbol 'xmlIsDigitGroup' because of 'dllexport' attribute
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/chvalid.h:156: error: uninitialized const 'xmlIsDigitGroup'
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/chvalid.h:176: error: external linkage required for symbol 'xmlIsExtenderGroup' because of 'dllexport' attribute
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/chvalid.h:176: error: uninitialized const 'xmlIsExtenderGroup'
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/chvalid.h:190: error: external linkage required for symbol 'xmlIsIdeographicGroup' because of 'dllexport' attribute
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/chvalid.h:190: error: uninitialized const 'xmlIsIdeographicGroup'
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/chvalid.h:191: error: external linkage required for symbol 'xmlIsPubidChar_tab' because of 'dllexport' attribute
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/chvalid.h:191: error: uninitialized const 'xmlIsPubidChar_tab'
In file included from testxml.cc:1:
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/parserInternals.h:279: error: external linkage required for symbol 'xmlStringText' because of 'dllexport' attribute
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/parserInternals.h:279: error: uninitialized const 'xmlStringText'
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/parserInternals.h:279: error: storage size of 'xmlStringText' isn't known
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/parserInternals.h:280: error: external linkage required for symbol 'xmlStringTextNoenc' because of 'dllexport' attribute
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/parserInternals.h:280: error: uninitialized const 'xmlStringTextNoenc'
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/parserInternals.h:280: error: storage size of 'xmlStringTextNoenc' isn't known
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/parserInternals.h:281: error: external linkage required for symbol 'xmlStringComment' because of 'dllexport' attribute
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/parserInternals.h:281: error: uninitialized const 'xmlStringComment'
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/parserInternals.h:281: error: storage size of 'xmlStringComment' isn't known


When compiling C source code, the compile error doesn't occur, just some warnings:

$ i686-pc-mingw32-gcc testxml.c -o testxml.exe -I /usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/parserInternals.h:279: warning: array 'xmlStringText' assumed to have one element
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/parserInternals.h:280: warning: array 'xmlStringTextNoenc' assumed to have one element
/usr/i686-pc-mingw32/sys-root/mingw/include/libxml2/libxml/parserInternals.h:281: warning: array 'xmlStringComment' assumed to have one element


When performing a small change in the headers, the compile error doesn't occur anymore:

--- xmlexports.h.orig	2009-09-25 00:00:03.511532978 +0200
+++ xmlexports.h	2009-09-25 00:00:15.684782702 +0200
@@ -139,7 +139,7 @@
@@ -115,7 +115,7 @@
    */
   #if !defined(LIBXML_STATIC)
     #define XMLPUBFUN __declspec(dllexport)
-    #define XMLPUBVAR __declspec(dllexport)
+    #define XMLPUBVAR __declspec(dllexport) extern
   #else
     #define XMLPUBFUN
     #if !defined(LIBXML_STATIC)