Index: src/backend/utils/adt/xml.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/utils/adt/xml.c,v
retrieving revision 1.83
diff -c -r1.83 xml.c
*** src/backend/utils/adt/xml.c	7 Jan 2009 13:44:37 -0000	1.83
--- src/backend/utils/adt/xml.c	22 Mar 2009 03:00:34 -0000
***************
*** 40,45 ****
--- 40,49 ----
   * not very good about specifying this, but for now we assume that
   * xmlCleanupParser() will get rid of anything we need to worry about.
   *
+  * libxml's original memory management callbacks are saved when we create
+  * LibxmlContext, and restored when we delete it.  This is so that there
+  * is some hope for other code (eg, plperl) to use libxml without crashing.
+  *
   * We use palloc --- which will throw a longjmp on error --- for allocation
   * callbacks that officially should act like malloc, ie, return NULL on
   * out-of-memory.  This is a bit risky since there is a chance of leaving
***************
*** 93,98 ****
--- 97,106 ----
  
  static StringInfo xml_err_buf = NULL;
  static MemoryContext LibxmlContext = NULL;
+ static xmlFreeFunc libxml_freeFunc = NULL;
+ static xmlMallocFunc libxml_mallocFunc = NULL;
+ static xmlReallocFunc libxml_reallocFunc = NULL;
+ static xmlStrdupFunc libxml_strdupFunc = NULL;
  
  static void xml_init(void);
  static void xml_memory_init(void);
***************
*** 1224,1237 ****
  	 * sure it doesn't go away before we've called xmlCleanupParser().
  	 */
  	if (LibxmlContext == NULL)
  		LibxmlContext = AllocSetContextCreate(TopMemoryContext,
  											  "LibxmlContext",
  											  ALLOCSET_DEFAULT_MINSIZE,
  											  ALLOCSET_DEFAULT_INITSIZE,
  											  ALLOCSET_DEFAULT_MAXSIZE);
  
! 	/* Re-establish the callbacks even if already set */
! 	xmlMemSetup(xml_pfree, xml_palloc, xml_repalloc, xml_pstrdup);
  }
  
  static void
--- 1232,1260 ----
  	 * sure it doesn't go away before we've called xmlCleanupParser().
  	 */
  	if (LibxmlContext == NULL)
+ 	{
+ 		/*
+ 		 * First, run xmlCleanupParser() to get rid of any libxml data
+ 		 * structures that exist now.  If there are any, they were created
+ 		 * with the native memory-management functions and will cause big
+ 		 * trouble if they're touched using our functions.
+ 		 */
+ 		xmlCleanupParser();
+ 
+ 		/* Next, save away libxml's native memory-management functions */
+ 		xmlMemGet(&libxml_freeFunc, &libxml_mallocFunc,
+ 				  &libxml_reallocFunc, &libxml_strdupFunc);
+ 
+ 		/* Create the context (note this could fail) */
  		LibxmlContext = AllocSetContextCreate(TopMemoryContext,
  											  "LibxmlContext",
  											  ALLOCSET_DEFAULT_MINSIZE,
  											  ALLOCSET_DEFAULT_INITSIZE,
  											  ALLOCSET_DEFAULT_MAXSIZE);
  
! 		/* Establish our memory management callbacks */
! 		xmlMemSetup(xml_pfree, xml_palloc, xml_repalloc, xml_pstrdup);
! 	}
  }
  
  static void
***************
*** 1242,1247 ****
--- 1265,1274 ----
  		/* Give libxml a chance to clean up dangling pointers */
  		xmlCleanupParser();
  
+ 		/* Restore native memory-management functions */
+ 		xmlMemSetup(libxml_freeFunc, libxml_mallocFunc,
+ 					libxml_reallocFunc, libxml_strdupFunc);
+ 
  		/* And flush the context */
  		MemoryContextDelete(LibxmlContext);
  		LibxmlContext = NULL;