SAX1: Align handling of default attributes with SAX2

The SAX1 parser is legacy code, but it seems more maintainable to align
it with SAX2.

include/private/parser.h

@@ -4,6 +4,8 @@
 #include <libxml/parser.h>
 #include <libxml/xmlversion.h>
 
+#include "private/dict.h"
+
 #define XML_INVALID_CHAR 0x200000
 
 #define XML_MAX_URI_LENGTH 2000
@@ -56,13 +58,35 @@
  */
 #define INPUT_CHUNK	250
 
+#define XML_SCAN_NC         1
+#define XML_SCAN_NMTOKEN    2
+#define XML_SCAN_OLD10      4
+
 struct _xmlAttrHashBucket {
     int index;
 };
 
-#define XML_SCAN_NC         1
-#define XML_SCAN_NMTOKEN    2
-#define XML_SCAN_OLD10      4
+typedef struct {
+    xmlHashedString prefix;
+    xmlHashedString name;
+    xmlHashedString value;
+    const xmlChar *valueEnd;
+    int external;
+    int expandedSize;
+} xmlDefAttr;
+
+typedef struct _xmlDefAttrs xmlDefAttrs;
+typedef xmlDefAttrs *xmlDefAttrsPtr;
+struct _xmlDefAttrs {
+    int nbAttrs;	/* number of defaulted attributes on that element */
+    int maxAttrs;       /* the size of the array */
+#if __STDC_VERSION__ >= 199901L
+    /* Using a C99 flexible array member avoids UBSan errors. */
+    xmlDefAttr attrs[] ATTRIBUTE_COUNTED_BY(maxAttrs);
+#else
+    xmlDefAttr attrs[1];
+#endif
+};
 
 XML_HIDDEN const xmlChar *
 xmlScanName(const xmlChar *buf, size_t maxSize, int flags);