Re: gettext and expat

[Bruno Haible]

Hi,

Jens Petersen wrote:
> Hi, finally got round to reporting this here:
> 
> Any thoughts on this issue from Red Hat bugzilla:
> 
>   https://bugzilla.redhat.com/show_bug.cgi?id=285701
> 
> it seems current gettext has problems with expat-2.0.x which moved to 
> libexpat.so.1 from libexpat.so.0.

Yes. It is fixed in CVS through the appended patch.

> I attach a patch by Nils which is included in coming Fedora 8 which 
> works around the issue.

It works around the issue, assuming a certain version of expat compiled
in a certain mode (namely, expat >= 2.0, compiled without -DXML_LARGE_SIZE).

In general, using expat.h when using dynamic loading is wrong, because
there are three possible ABIs of libexpat (version < 2.0,
version >= 2.0 default, version >= 2.0 with -DXML_LARGE_SIZE),
and the include file that you include at compile time is
unrelated to the library that will be found at run time.

Your workaround assumes a particular ABI (which may be OK in the context
of a particular Linux distribution). The appended patch works with all 3 ABIs.
It will be contained in gettext-0.16.2.

Bruno


diff -c -3 -r1.19 -r1.20
*** gettext-tools/src/x-glade.c 19 Feb 2007 03:31:37 -0000      1.19
--- gettext-tools/src/x-glade.c 2 Sep 2007 16:07:49 -0000       1.20
***************
*** 26,31 ****
--- 26,32 ----
  
  #include <errno.h>
  #include <stdbool.h>
+ #include <stdint.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
***************
*** 109,118 ****
--- 110,212 ----
  }
  
  
+ /* ======================= Different libexpat ABIs.  ======================= 
*/
+ 
+ /* There are three different ABIs of libexpat, regarding the functions
+    XML_GetCurrentLineNumber and XML_GetCurrentColumnNumber.
+    In expat < 2.0, they return an 'int'.
+    In expat >= 2.0, they return
+      - a 'long' if expat was compiled with the default flags, or
+      - a 'long long' if expat was compiled with -DXML_LARGE_SIZE.
+    But the <expat.h> include file does not contain the information whether
+    expat was compiled with -DXML_LARGE_SIZE; so the include file is lying!
+    For this information, we need to call XML_GetFeatureList(), for
+    expat >= 2.0.1; for expat = 2.0.0, we have to assume the default flags.  */
+ 
+ #if !DYNLOAD_LIBEXPAT
+ 
+ # if XML_MAJOR_VERSION >= 2
+ 
+ /* expat >= 2.0 -> Return type is 'int64_t' worst-case.  */
+ 
+ /* Put the function pointers into variables, because some GCC 4 versions
+    generate an abort when we convert symbol address to different function
+    pointer types.  */
+ static void *p_XML_GetCurrentLineNumber = (void *) &XML_GetCurrentLineNumber;
+ static void *p_XML_GetCurrentColumnNumber = (void *) 
&XML_GetCurrentColumnNumber;
+ 
+ /* Return true if libexpat was compiled with -DXML_LARGE_SIZE.  */
+ static bool
+ is_XML_LARGE_SIZE_ABI (void)
+ {
+   static bool tested;
+   static bool is_large;
+ 
+   if (!tested)
+     {
+       const XML_Feature *features;
+ 
+       is_large = false;
+       for (features = XML_GetFeatureList (); features->name != NULL; 
features++)
+       if (strcmp (features->name, "XML_LARGE_SIZE") == 0)
+         {
+           is_large = true;
+           break;
+         }
+ 
+       tested = true;
+     }
+   return is_large;
+ }
+ 
+ static int64_t
+ GetCurrentLineNumber (XML_Parser parser)
+ {
+   if (is_XML_LARGE_SIZE_ABI ())
+     return ((int64_t (*) (XML_Parser)) p_XML_GetCurrentLineNumber) (parser);
+   else
+     return ((long (*) (XML_Parser)) p_XML_GetCurrentLineNumber) (parser);
+ }
+ #  define XML_GetCurrentLineNumber GetCurrentLineNumber
+ 
+ static int64_t
+ GetCurrentColumnNumber (XML_Parser parser)
+ {
+   if (is_XML_LARGE_SIZE_ABI ())
+     return ((int64_t (*) (XML_Parser)) p_XML_GetCurrentColumnNumber) (parser);
+   else
+     return ((long (*) (XML_Parser)) p_XML_GetCurrentColumnNumber) (parser);
+ }
+ #  define XML_GetCurrentColumnNumber GetCurrentColumnNumber
+ 
+ # else
+ 
+ /* expat < 2.0 -> Return type is 'int'.  */
+ 
+ # endif
+ 
+ #endif
+ 
+ 
  /* ===================== Dynamic loading of libexpat.  ===================== 
*/
  
  #if DYNLOAD_LIBEXPAT
  
+ typedef struct
+   {
+     int major;
+     int minor;
+     int micro;
+   }
+   XML_Expat_Version;
+ enum XML_FeatureEnum { XML_FEATURE_END = 0 };
+ typedef struct
+   {
+     enum XML_FeatureEnum feature;
+     const char *name;
+     long int value;
+   }
+   XML_Feature;
  typedef void *XML_Parser;
  typedef char XML_Char;
  typedef char XML_LChar;
***************
*** 122,151 ****
  typedef void (*XML_CharacterDataHandler) (void *userData, const XML_Char *s, 
int len);
  typedef void (*XML_CommentHandler) (void *userData, const XML_Char *data);
  
  static XML_Parser (*p_XML_ParserCreate) (const XML_Char *encoding);
  static void (*p_XML_SetElementHandler) (XML_Parser parser, 
XML_StartElementHandler start, XML_EndElementHandler end);
  static void (*p_XML_SetCharacterDataHandler) (XML_Parser parser, 
XML_CharacterDataHandler handler);
  static void (*p_XML_SetCommentHandler) (XML_Parser parser, XML_CommentHandler 
handler);
  static int (*p_XML_Parse) (XML_Parser parser, const char *s, int len, int 
isFinal);
  static enum XML_Error (*p_XML_GetErrorCode) (XML_Parser parser);
! #if XML_MAJOR_VERSION >= 2
! static XML_Size (*p_XML_GetCurrentLineNumber) (XML_Parser parser);
! static XML_Size (*p_XML_GetCurrentColumnNumber) (XML_Parser parser);
! #else
! static int (*p_XML_GetCurrentLineNumber) (XML_Parser parser);
! static int (*p_XML_GetCurrentColumnNumber) (XML_Parser parser);
! #endif
  static void (*p_XML_ParserFree) (XML_Parser parser);
  static const XML_LChar * (*p_XML_ErrorString) (int code);
  
  #define XML_ParserCreate (*p_XML_ParserCreate)
  #define XML_SetElementHandler (*p_XML_SetElementHandler)
  #define XML_SetCharacterDataHandler (*p_XML_SetCharacterDataHandler)
  #define XML_SetCommentHandler (*p_XML_SetCommentHandler)
  #define XML_Parse (*p_XML_Parse)
  #define XML_GetErrorCode (*p_XML_GetErrorCode)
! #define XML_GetCurrentLineNumber (*p_XML_GetCurrentLineNumber)
! #define XML_GetCurrentColumnNumber (*p_XML_GetCurrentColumnNumber)
  #define XML_ParserFree (*p_XML_ParserFree)
  #define XML_ErrorString (*p_XML_ErrorString)
  
--- 216,309 ----
  typedef void (*XML_CharacterDataHandler) (void *userData, const XML_Char *s, 
int len);
  typedef void (*XML_CommentHandler) (void *userData, const XML_Char *data);
  
+ static XML_Expat_Version (*p_XML_ExpatVersionInfo) (void);
+ static const XML_Feature * (*p_XML_GetFeatureList) (void);
  static XML_Parser (*p_XML_ParserCreate) (const XML_Char *encoding);
  static void (*p_XML_SetElementHandler) (XML_Parser parser, 
XML_StartElementHandler start, XML_EndElementHandler end);
  static void (*p_XML_SetCharacterDataHandler) (XML_Parser parser, 
XML_CharacterDataHandler handler);
  static void (*p_XML_SetCommentHandler) (XML_Parser parser, XML_CommentHandler 
handler);
  static int (*p_XML_Parse) (XML_Parser parser, const char *s, int len, int 
isFinal);
  static enum XML_Error (*p_XML_GetErrorCode) (XML_Parser parser);
! static void *p_XML_GetCurrentLineNumber;
! static void *p_XML_GetCurrentColumnNumber;
  static void (*p_XML_ParserFree) (XML_Parser parser);
  static const XML_LChar * (*p_XML_ErrorString) (int code);
  
+ #define XML_ExpatVersionInfo (*p_XML_ExpatVersionInfo)
+ #define XML_GetFeatureList (*p_XML_GetFeatureList)
+ 
+ enum XML_Size_ABI { is_int, is_long, is_int64_t };
+ 
+ static enum XML_Size_ABI
+ get_XML_Size_ABI (void)
+ {
+   static bool tested;
+   static enum XML_Size_ABI abi;
+ 
+   if (!tested)
+     {
+       if (XML_ExpatVersionInfo () .major >= 2)
+       /* expat >= 2.0 -> XML_Size is 'int64_t' or 'long'.  */
+       {
+         const XML_Feature *features;
+ 
+         abi = is_long;
+         for (features = XML_GetFeatureList ();
+              features->name != NULL;
+              features++)
+           if (strcmp (features->name, "XML_LARGE_SIZE") == 0)
+             {
+               abi = is_int64_t;
+               break;
+             }
+       }
+       else
+       /* expat < 2.0 -> XML_Size is 'int'.  */
+       abi = is_int;
+       tested = true;
+     }
+   return abi;
+ }
+ 
  #define XML_ParserCreate (*p_XML_ParserCreate)
  #define XML_SetElementHandler (*p_XML_SetElementHandler)
  #define XML_SetCharacterDataHandler (*p_XML_SetCharacterDataHandler)
  #define XML_SetCommentHandler (*p_XML_SetCommentHandler)
  #define XML_Parse (*p_XML_Parse)
  #define XML_GetErrorCode (*p_XML_GetErrorCode)
! 
! static int64_t
! XML_GetCurrentLineNumber (XML_Parser parser)
! {
!   switch (get_XML_Size_ABI ())
!     {
!     case is_int:
!       return ((int (*) (XML_Parser)) p_XML_GetCurrentLineNumber) (parser);
!     case is_long:
!       return ((long (*) (XML_Parser)) p_XML_GetCurrentLineNumber) (parser);
!     case is_int64_t:
!       return ((int64_t (*) (XML_Parser)) p_XML_GetCurrentLineNumber) (parser);
!     default:
!       abort ();
!     }
! }
! 
! static int64_t
! XML_GetCurrentColumnNumber (XML_Parser parser)
! {
!   switch (get_XML_Size_ABI ())
!     {
!     case is_int:
!       return ((int (*) (XML_Parser)) p_XML_GetCurrentColumnNumber) (parser);
!     case is_long:
!       return ((long (*) (XML_Parser)) p_XML_GetCurrentColumnNumber) (parser);
!     case is_int64_t:
!       return ((int64_t (*) (XML_Parser)) p_XML_GetCurrentColumnNumber) 
(parser);
!     default:
!       abort ();
!     }
! }
! 
  #define XML_ParserFree (*p_XML_ParserFree)
  #define XML_ErrorString (*p_XML_ErrorString)
  
***************
*** 157,170 ****
    if (libexpat_loaded == 0)
      {
        void *handle;
!       /* Be careful to use exactly the version of libexpat that matches the
!        binary interface declared in <expat.h>.  */
! #if XML_MAJOR_VERSION >= 2
        handle = dlopen ("libexpat.so.1", RTLD_LAZY);
! #else
!       handle = dlopen ("libexpat.so.0", RTLD_LAZY);
! #endif
        if (handle != NULL
          && (p_XML_ParserCreate =
                (XML_Parser (*) (const XML_Char *))
                dlsym (handle, "XML_ParserCreate")) != NULL
--- 315,333 ----
    if (libexpat_loaded == 0)
      {
        void *handle;
! 
!       /* Try to load libexpat-2.x.  */
        handle = dlopen ("libexpat.so.1", RTLD_LAZY);
!       if (handle == NULL)
!       /* Try to load libexpat-1.x.  */
!       handle = dlopen ("libexpat.so.0", RTLD_LAZY);
        if (handle != NULL
+         && (p_XML_ExpatVersionInfo =
+               (XML_Expat_Version (*) (void))
+               dlsym (handle, "XML_ExpatVersionInfo")) != NULL
+         && (p_XML_GetFeatureList =
+               (const XML_Feature * (*) (void))
+               dlsym (handle, "XML_GetFeatureList")) != NULL
          && (p_XML_ParserCreate =
                (XML_Parser (*) (const XML_Char *))
                dlsym (handle, "XML_ParserCreate")) != NULL
***************
*** 184,201 ****
                (enum XML_Error (*) (XML_Parser))
                dlsym (handle, "XML_GetErrorCode")) != NULL
          && (p_XML_GetCurrentLineNumber =
- #if XML_MAJOR_VERSION >= 2
-               (XML_Size (*) (XML_Parser))
- #else
-               (int (*) (XML_Parser))
- #endif
                dlsym (handle, "XML_GetCurrentLineNumber")) != NULL
          && (p_XML_GetCurrentColumnNumber =
- #if XML_MAJOR_VERSION >= 2
-               (XML_Size (*) (XML_Parser))
- #else
-               (int (*) (XML_Parser))
- #endif
                dlsym (handle, "XML_GetCurrentColumnNumber")) != NULL
          && (p_XML_ParserFree =
                (void (*) (XML_Parser))
--- 347,354 ----