Fix crash in bytea-to-XML mapping when the source value is toasted.

Report and fix by Michael McMaster.  Some minor code beautification by me,
also avoid memory leaks in the special-case paths.

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 1.77 2008/09/16 00:49:41 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.78 2008/10/09 15:49:04 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1568,8 +1568,6 @@ map_sql_value_to_xml_value(Datum value, Oid type)
 {
 	StringInfoData buf;
 
-	initStringInfo(&buf);
-
 	if (type_is_array(type))
 	{
 		ArrayType  *array;
@@ -1591,6 +1589,8 @@ map_sql_value_to_xml_value(Datum value, Oid type)
 						  &elem_values, &elem_nulls,
 						  &num_elems);
 
+		initStringInfo(&buf);
+
 		for (i = 0; i < num_elems; i++)
 		{
 			if (elem_nulls[i])
@@ -1604,6 +1604,8 @@ map_sql_value_to_xml_value(Datum value, Oid type)
 
 		pfree(elem_values);
 		pfree(elem_nulls);
+
+		return buf.data;
 	}
 	else
 	{
@@ -1687,17 +1689,11 @@ map_sql_value_to_xml_value(Datum value, Oid type)
 
 					return pstrdup(buf);
 				}
-		}
-
-		getTypeOutputInfo(type, &typeOut, &isvarlena);
-		str = OidOutputFunctionCall(typeOut, value);
-
-		if (type == XMLOID)
-			return str;
 
 #ifdef USE_LIBXML
-		if (type == BYTEAOID)
+			case BYTEAOID:
 				{
+					bytea	   *bstr = DatumGetByteaPP(value);
 					xmlBufferPtr buf;
 					xmlTextWriterPtr writer;
 					char	   *result;
@@ -1708,9 +1704,11 @@ map_sql_value_to_xml_value(Datum value, Oid type)
 					writer = xmlNewTextWriterMemory(buf, 0);
 
 					if (xmlbinary == XMLBINARY_BASE64)
-				xmlTextWriterWriteBase64(writer, VARDATA(value), 0, VARSIZE(value) - VARHDRSZ);
+						xmlTextWriterWriteBase64(writer, VARDATA_ANY(bstr),
+												 0, VARSIZE_ANY_EXHDR(bstr));
 					else
-				xmlTextWriterWriteBinHex(writer, VARDATA(value), 0, VARSIZE(value) - VARHDRSZ);
+						xmlTextWriterWriteBinHex(writer, VARDATA_ANY(bstr),
+												 0, VARSIZE_ANY_EXHDR(bstr));
 
 					xmlFreeTextWriter(writer);
 					result = pstrdup((const char *) xmlBufferContent(buf));
@@ -1719,30 +1717,45 @@ map_sql_value_to_xml_value(Datum value, Oid type)
 				}
 #endif   /* USE_LIBXML */
 
-		for (p = str; *p; p += pg_mblen(p))
+		}
+
+		/*
+		 * otherwise, just use the type's native text representation
+		 */
+		getTypeOutputInfo(type, &typeOut, &isvarlena);
+		str = OidOutputFunctionCall(typeOut, value);
+
+		/* ... exactly as-is for XML */
+		if (type == XMLOID)
+			return str;
+
+		/* otherwise, translate special characters as needed */
+		initStringInfo(&buf);
+
+		for (p = str; *p; p++)
 		{
 			switch (*p)
 			{
 				case '&':
-					appendStringInfo(&buf, "&amp;");
+					appendStringInfoString(&buf, "&amp;");
 					break;
 				case '<':
-					appendStringInfo(&buf, "&lt;");
+					appendStringInfoString(&buf, "&lt;");
 					break;
 				case '>':
-					appendStringInfo(&buf, "&gt;");
+					appendStringInfoString(&buf, "&gt;");
 					break;
 				case '\r':
-					appendStringInfo(&buf, "&#x0d;");
+					appendStringInfoString(&buf, "&#x0d;");
 					break;
 				default:
-					appendBinaryStringInfo(&buf, p, pg_mblen(p));
+					appendStringInfoCharMacro(&buf, *p);
 					break;
 			}
 		}
-	}
 
 		return buf.data;
+	}
 }