It turns out the LIBXML_TEST_VERSION macro calls xmlInitParser().

tglsfdc · tglsfdc · commit 1bbf8706ae6e · 2008-01-12T21:14:08.000Z
Therefore we must xmlCleanupParser(), or we risk leaving behind
dangling pointers to whatever memory context is current when xml_init()
is called.  This seems to fix bug #3860, though we might still want
the more invasive solution being worked on by Alvaro.
diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.66 2008/01/12 10:50:03 neilc Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.67 2008/01/12 21:14:08 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -958,6 +958,9 @@ xml_init(void)
 		/* Check library compatibility */
 		LIBXML_TEST_VERSION;
 
+		/* The above calls xmlInitParser(); must clean up dangling pointers */
+		xmlCleanupParser();
+
 		first_time = false;
 	}
 	else

Original file line number	Diff line number	Diff line change
`@@ -7,7 +7,7 @@`
`7`	`7`	`* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group`
`8`	`8`	`* Portions Copyright (c) 1994, Regents of the University of California`
`9`	`9`	`*`
`10`		`- * $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.66 2008/01/12 10:50:03 neilc Exp $`
	`10`	`+ * $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.67 2008/01/12 21:14:08 tgl Exp $`
`11`	`11`	`*`
`12`	`12`	`*-------------------------------------------------------------------------`
`13`	`13`	`*/`
`@@ -958,6 +958,9 @@ xml_init(void)`
`958`	`958`	`/* Check library compatibility */`
`959`	`959`	`LIBXML_TEST_VERSION;`
`960`	`960`
	`961`	`+ /* The above calls xmlInitParser(); must clean up dangling pointers */`
	`962`	`+ xmlCleanupParser();`
	`963`	`+`
`961`	`964`	`first_time = false;`
`962`	`965`	`}`
`963`	`966`	`else`